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From the Archives of the AFIP

Cerebral Intraventricular Neoplasms: Radiologic-Pathologic Correlation¹

¹ From the Departments of Radiologic Pathology (K.K.K.) and Neuropathology (G.D.S.), Armed Forces Institute of Pathology, 14th St at Alaska Ave, Bldg 54, Room M-121, Washington, DC 20306-6000; and the Departments of Radiology and Nuclear Medicine, Uniformed Services University of the Health Sciences, Bethesda, Md (K.K.K.). Received July 3, 2002; revision requested July 15 and received August 6; accepted August 20. Address correspondence to K.K.K. (e-mail: koeller@afip.osd.mil).

	Abstract

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Neoplasms of the Ventricular... Neoplasms of the Choroid... Summary References

 
Intraventricular neoplasms are readily seen on cross-sectional images, but the myriad possibilities may make a focused differential diagnosis elusive. Consideration of the tissue within and composing the ventricular lining and the clinical findings provide the means to limit the differential diagnosis when analyzing an intraventricular mass on an imaging study. Ependymomas are typically calcified, are more common in children, are more common in the fourth ventricle, and show intense enhancement on contrast-enhanced images. Subependymomas and central neurocytomas have an affinity for the anterior portion of the lateral ventricle, and both commonly demonstrate a heterogeneous cystic appearance on cross-sectional images. Subependymomas are more common in older adults, whereas central neurocytomas are more common before 40 years of age. Subependymal giant cell astrocytomas always lie near the foramen of Monro and are characterized by frequent calcification, intense enhancement on contrast-enhanced studies, and the presence of other stigmata seen in tuberous sclerosis. When a mass is centered on the choroid plexus, a highly vascular tumor—either choroid plexus papilloma, choroid plexus carcinoma, meningioma, or metastasis—should be suspected. The characteristic heavily lobulated appearance of a choroid plexus tumor favors this diagnosis over other possibilities, although it is not always possible to distinguish between the more common benign form, the choroid plexus papilloma, and the less common malignant counterpart, the choroid plexus carcinoma. By using clinical, demographic, and imaging findings, one can significantly limit the differential diagnosis for many of the most common intraventricular neoplasms.

Index Terms: Astrocytoma, 1612.1832, 1612.3639 • Brain neoplasms, 16.36, 161.38 • Choroid plexus, neoplasms, 1617.3639 • Ependymoma, 161.3636, 164.3636 • Meninges, neoplasms, 161.366 • Neurocytoma, 161.369

	LEARNING OBJECTIVES FOR TEST 6

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Neoplasms of the Ventricular... Neoplasms of the Choroid... Summary References

 
After reading this article and taking the test, the reader will be able to:

• Describe the distinguishing imaging features of common cerebral intraventricular neoplasms.
  
• Identify the characteristic imaging appearances of the different types of intraventricular tumors that allow a specific diagnosis to be favored.
  
• Discuss the direct correlation of the imaging appearance with the gross pathologic appearance in cerebral intraventricular neoplasms.
  

	Introduction

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Neoplasms of the Ventricular... Neoplasms of the Choroid... Summary References

 
Neoplasms that arise within the cerebral ventricular system are especially conspicuous on cross-sectional images, in part because of the great contrast between these soft-tissue masses and the surrounding cerebrospinal fluid (CSF). Although they are relatively easy to visualize, it is more difficult to narrow the differential diagnosis for a lesion in this location without knowledge of the tissue types that give rise to these tumors. In this article, eight of the more common lesions to arise in this area of the brain are reviewed, by using case material from the Thompson Archives of the Department of Radiologic Pathology at the Armed Forces Institute of Pathology and with the tissue of origin used as a guide.

The ventricles are surrounded by a lining of ependymal cells and a subependymal plate composed of glial cells. Accordingly, these layers give rise to ependymomas, subependymomas, and subependymal giant cell astrocytomas (SEGAs). This lining and the septum pellucidum, a glial-lined structure, also give rise to a glial neuronal tumor, the central neurocytoma that is unique to the ventricular system. Central neurocytoma is a recently described tumor that, until its confirmation with electron microscopy, was frequently mistaken for an intraventricular oligodendroglioma with light microscopy. A central neurocytoma has a striking resemblance to a subependymoma on radiologic images. The central neurocytoma and SEGA predominate in the anterior portion of the lateral ventricle near the foramen of Monro, whereas the ependymoma and subependymoma are usually found in either the fourth or lateral ventricles. The choroid plexus is the most highly vascular portion of the ventricular system and produces CSF. Neoplasms from this tissue are highly vascular and commonly associated with hydrocephalus. They occur in a benign form, the choroid plexus papilloma, and less commonly, in a malignant counterpart, the choroid plexus carcinoma. Tumors, such as meningioma and metastatic disease, that are commonly associated with a generous vascular supply also arise from this site. Since the choroid plexus is most prominent in the atria, these masses are most commonly noted in the posterior portion of the lateral ventricles. Salient demographic and imaging features of these eight tumor types are listed in the Table.

	Neoplasms of the Ventricular Wall and Septum Pellucidum

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Neoplasms of the Ventricular... Neoplasms of the Choroid... Summary References

Ependymomas may manifest at any age, with a documented age range of 1 month to 81 years (1). There is no gender predilection (1). Most posterior fossa ependymomas arise in children, with a mean age of about 6 years (1). The mean age at presentation is higher for patients who have a supratentorial ependymoma (18–24 years) (2). Of those ependymomas that occur intraventricularly, 58% originate in the fourth ventricle, whereas the remaining 42% are located in the lateral and third ventricles (3). Supratentorial ependymomas are more commonly extraventricular, especially in children (1,2). It is speculated that ependymomas may arise from embryonic rests of ependymal tissue trapped within the developing cerebral hemispheres (1). Bizarre sites reported for ependymomas include the ovaries, soft tissues, mediastinum, and sacrococcygeal region (4).

As with other intraventricular masses, clinical signs and symptoms are largely secondary to the effects of increased intracranial pressure and hydrocephalus (1). Because the fourth ventricle is a predominant site for these tumors, some patients may present with cerebellar ataxia and paresis (1,5). Patients with supratentorial ependymomas tend to present with focal neurologic deficits and seizures (1). In general, children with ependymomas have a less favorable prognosis than adults, in part from the increased prevalence of a fourth ventricle location and the predilection of this group for more anaplastic forms of the disease (1).

The 5-year progression-free rate for children overall is about 50% (6), with children younger than 2 years having an especially poor prognosis (7). The 5-year and 10-year survival rates for adults are 57.1% and 45%, respectively (1). The treatment of choice is gross total resection, and the degree of resection directly correlates with a better prognosis (8). Patients with supratentorial ependymomas have a better survival rate than those patients with posterior fossa ependymomas (9). For all types of ependymomas, recurrence is common (2,10). Postoperative radiation therapy is advocated for partially resected ependymomas (10).

Intraventricular ependymomas are well-circumscribed, grayish-red masses that usually fill the ventricular lumen and occasionally may extend into the adjacent brain parenchyma (Fig 1) (1). When they arise in the fourth ventricle, these soft pliable tumors originate from the floor or roof of the ventricle and frequently extend through the foramen of Luschka into the cerebellopontine angle and even the foramen magnum (Fig 2) (1).

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 1.  Ependymoma. Photograph of an autopsy specimen sectioned through the level of the fourth ventricle shows a soft, friable heterogeneous mass (arrows) within the fourth ventricle. Scattered areas of hemorrhage are noted.

View larger version (200K): [in this window] [in a new window] [Download PPT slide]   Figure 2.  Ependymoma. Photograph of a brain at autopsy shows extensive cerebellopontine angle extension (arrows) from a fourth ventricular ependymoma. Numerous areas of hemorrhage give the mass a heterogeneous appearance.

View larger version (175K): [in this window] [in a new window] [Download PPT slide]   Figure 3.  Ependymoma. Photomicrograph (original magnification, x100; hematoxylin-eosin stain) of an ependymoma shows a moderately cellular matrix composed of glial cells with perivascular rosettes (arrowheads) and no mitotic figures.

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.  Ependymoma in a 16-month-old child. (a) Axial CT image shows a fourth ventricular mass that is slightly hyperattenuated compared with the surrounding cerebellum. Focal calcification (arrow) is noted. (b) Axial T1-weighted magnetic resonance (MR) image shows the mildly heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted image, the mass is hyperintense compared with the cerebellum, with no surrounding vasogenic edema. (d) On a contrast-enhanced axial T1-weighted image, the mass shows intense heterogeneous enhancement.

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.  Ependymoma in a 16-month-old child. (a) Axial CT image shows a fourth ventricular mass that is slightly hyperattenuated compared with the surrounding cerebellum. Focal calcification (arrow) is noted. (b) Axial T1-weighted magnetic resonance (MR) image shows the mildly heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted image, the mass is hyperintense compared with the cerebellum, with no surrounding vasogenic edema. (d) On a contrast-enhanced axial T1-weighted image, the mass shows intense heterogeneous enhancement.

View larger version (157K): [in this window] [in a new window] [Download PPT slide]   Figure 4c.  Ependymoma in a 16-month-old child. (a) Axial CT image shows a fourth ventricular mass that is slightly hyperattenuated compared with the surrounding cerebellum. Focal calcification (arrow) is noted. (b) Axial T1-weighted magnetic resonance (MR) image shows the mildly heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted image, the mass is hyperintense compared with the cerebellum, with no surrounding vasogenic edema. (d) On a contrast-enhanced axial T1-weighted image, the mass shows intense heterogeneous enhancement.

View larger version (148K): [in this window] [in a new window] [Download PPT slide]   Figure 4d.  Ependymoma in a 16-month-old child. (a) Axial CT image shows a fourth ventricular mass that is slightly hyperattenuated compared with the surrounding cerebellum. Focal calcification (arrow) is noted. (b) Axial T1-weighted magnetic resonance (MR) image shows the mildly heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted image, the mass is hyperintense compared with the cerebellum, with no surrounding vasogenic edema. (d) On a contrast-enhanced axial T1-weighted image, the mass shows intense heterogeneous enhancement.

View larger version (170K): [in this window] [in a new window] [Download PPT slide]   Figure 5a.  Malignant ependymoma in a 58-year-old woman with a history of ductal carcinoma and renal cell carcinoma. (a) Axial CT image shows a heterogeneously hypoattenuated mass (arrows) adjacent to the right frontal horn of the lateral ventricle. (b) Axial T1-weighted MR image shows the heterogeneous mass, with cystlike areas mixed with more hyperintense regions. (c) On an axial T2-weighted MR image, the mass is predominantly hyperintense with focal regions of more hypointense signal. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense but heterogeneous enhancement. At surgery, the mass involved both the lateral ventricle and the right frontal lobe. Histologic examination revealed ependymoma.

View larger version (184K): [in this window] [in a new window] [Download PPT slide]   Figure 5b.  Malignant ependymoma in a 58-year-old woman with a history of ductal carcinoma and renal cell carcinoma. (a) Axial CT image shows a heterogeneously hypoattenuated mass (arrows) adjacent to the right frontal horn of the lateral ventricle. (b) Axial T1-weighted MR image shows the heterogeneous mass, with cystlike areas mixed with more hyperintense regions. (c) On an axial T2-weighted MR image, the mass is predominantly hyperintense with focal regions of more hypointense signal. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense but heterogeneous enhancement. At surgery, the mass involved both the lateral ventricle and the right frontal lobe. Histologic examination revealed ependymoma.

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 5c.  Malignant ependymoma in a 58-year-old woman with a history of ductal carcinoma and renal cell carcinoma. (a) Axial CT image shows a heterogeneously hypoattenuated mass (arrows) adjacent to the right frontal horn of the lateral ventricle. (b) Axial T1-weighted MR image shows the heterogeneous mass, with cystlike areas mixed with more hyperintense regions. (c) On an axial T2-weighted MR image, the mass is predominantly hyperintense with focal regions of more hypointense signal. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense but heterogeneous enhancement. At surgery, the mass involved both the lateral ventricle and the right frontal lobe. Histologic examination revealed ependymoma.

View larger version (175K): [in this window] [in a new window] [Download PPT slide]   Figure 5d.  Malignant ependymoma in a 58-year-old woman with a history of ductal carcinoma and renal cell carcinoma. (a) Axial CT image shows a heterogeneously hypoattenuated mass (arrows) adjacent to the right frontal horn of the lateral ventricle. (b) Axial T1-weighted MR image shows the heterogeneous mass, with cystlike areas mixed with more hyperintense regions. (c) On an axial T2-weighted MR image, the mass is predominantly hyperintense with focal regions of more hypointense signal. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense but heterogeneous enhancement. At surgery, the mass involved both the lateral ventricle and the right frontal lobe. Histologic examination revealed ependymoma.

View larger version (182K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.  Ependymoma in a 29-year-old adult. (a) Sagittal T1-weighted MR image shows an isointense fourth ventricular mass (arrows) with inferior extension through the foramen magnum. (b) On an axial T2-weighted MR image, the mass is mildly hyperintense compared with the cerebellum and extends through the right foramen of Luschka into the cerebellopontine angle. (c) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense but heterogeneous enhancement.

View larger version (172K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.  Ependymoma in a 29-year-old adult. (a) Sagittal T1-weighted MR image shows an isointense fourth ventricular mass (arrows) with inferior extension through the foramen magnum. (b) On an axial T2-weighted MR image, the mass is mildly hyperintense compared with the cerebellum and extends through the right foramen of Luschka into the cerebellopontine angle. (c) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense but heterogeneous enhancement.

View larger version (175K): [in this window] [in a new window] [Download PPT slide]   Figure 6c.  Ependymoma in a 29-year-old adult. (a) Sagittal T1-weighted MR image shows an isointense fourth ventricular mass (arrows) with inferior extension through the foramen magnum. (b) On an axial T2-weighted MR image, the mass is mildly hyperintense compared with the cerebellum and extends through the right foramen of Luschka into the cerebellopontine angle. (c) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense but heterogeneous enhancement.

Subependymoma
In 1945, Scheinker (15) described seven cases of brain tumors arising from the subependymal glial layer surrounding the cerebral ventricles. These tumors were characterized by expansive growth and lacked an infiltrative pattern at histologic examination. Since that time, more than 100 similar cases have been reported in the literature. With the exception of a very small number of cases that occurred in the brain parenchyma, cerebellopontine angle, and spinal cord, the overwhelming majority of these tumors have occurred within the fourth and lateral ventricles (2,5,15–25). The true incidence of subependymomas is difficult to ascertain because many of the cases occurred in asymptomatic patients and were detected only incidentally at autopsy. In a review of 1,000 serial necropsies in asymptomatic patients, Matsumura at al (17) reported the prevalence as 0.4%, compared with a prevalence of 0.7% in 1,000 consecutive craniotomies performed in symptomatic patients. Despite four case reports of subependymomas occurring in siblings, including one set of identical twins, no genetic susceptibility for the tumor has been proved (19,21,26).

Most subependymomas are smaller than 2 cm in diameter (26). However, symptomatic subependymomas are usually larger, averaging about 3–5 cm in greatest dimension (5,22). Symptoms most commonly depend on the location and size of the tumor, with intratumoral hemorrhage being another possible influence (5). The clinical presentation is nonspecific. Most symptomatic patients (80%) present with symptoms related to hydrocephalus as a consequence of ventricular obstruction (16,26). Less commonly, focal neurologic deficits (27% of cases), seizures (9%), and subarachnoid hemorrhage (4.5%) have been reported (16).

Males are more commonly affected, and most reported cases (82%) have occurred in patients older than 15 years (16,26). At least half of the reported cases have occurred in the fourth ventricle, with most of the remainder arising in the lateral ventricle (2,5,15–26). In rare cases, subependymomas have been recorded arising from the septum pellucidum, the third ventricle, and in the cervical or cervicothoracic spinal cord (16, 23). Gross total surgical resection is the goal of therapy (16). Even if only partial resection is achieved, postoperative radiation therapy or chemotherapy is usually not indicated. Recurrence after surgical resection is rare (2,22).

Subependymomas have a white to grayish color and are well circumscribed with a firm texture (16). The tumors grow in a slow deliberate fashion, are usually avascular, and are attached to the ventricular wall by a narrow pedicle (16). Although the exact histogenesis is still uncertain, they most likely arise from subependymal glial cells (26). Other possible sites include astrocytes from the subependymal plate, ependymal cells, and a mixture of ependymal and astrocytic cells (26).

A dense fibrillary matrix interrupted by numerous small cysts and nests of isomorphic nuclei that resemble subependymal glia is typically seen at histologic examination (Fig 7) (26). Mitotic activity is usually low or absent; thus, subependymomas correspond histologically to WHO grade I (26). Although most tumors are pure subependymomas, about 10% may manifest as an admixture with an ependymoma (5,16,26). In addition, other reported combinations include those with melanin, rhabdomyosarcoma, and sarcomatous transformation of vascular stromal elements (26). The prognosis of a patient with an intraventricular subependymoma is good, with gross surgical resection being curative (26). A good clinical outcome is less certain when the tumor is mixed with an ependymoma (5).

View larger version (235K): [in this window] [in a new window] [Download PPT slide]   Figure 7.  Subependymoma. Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a subependymoma shows scattered clusters of nuclei (arrowheads) separated by large, acellular regions of glial processes.

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.  Subependymoma in a 53-year-old man. (a) Axial CT image shows a right frontal horn mass that is predominantly isoattenuated compared with the brain parenchyma. Curvilinear calcification (arrow) is seen. (b) Axial T1-weighted MR image shows isointensity within the mass, compared with the white matter. (c) Axial T2-weighted MR image shows heterogeneous hyperintensity within the mass and no evidence of periventricular edema. (d) Contrast-enhanced axial T1-weighted MR image shows scattered heterogeneous enhancement within the mass.

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.  Subependymoma in a 53-year-old man. (a) Axial CT image shows a right frontal horn mass that is predominantly isoattenuated compared with the brain parenchyma. Curvilinear calcification (arrow) is seen. (b) Axial T1-weighted MR image shows isointensity within the mass, compared with the white matter. (c) Axial T2-weighted MR image shows heterogeneous hyperintensity within the mass and no evidence of periventricular edema. (d) Contrast-enhanced axial T1-weighted MR image shows scattered heterogeneous enhancement within the mass.

View larger version (164K): [in this window] [in a new window] [Download PPT slide]   Figure 8c.  Subependymoma in a 53-year-old man. (a) Axial CT image shows a right frontal horn mass that is predominantly isoattenuated compared with the brain parenchyma. Curvilinear calcification (arrow) is seen. (b) Axial T1-weighted MR image shows isointensity within the mass, compared with the white matter. (c) Axial T2-weighted MR image shows heterogeneous hyperintensity within the mass and no evidence of periventricular edema. (d) Contrast-enhanced axial T1-weighted MR image shows scattered heterogeneous enhancement within the mass.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 8d.  Subependymoma in a 53-year-old man. (a) Axial CT image shows a right frontal horn mass that is predominantly isoattenuated compared with the brain parenchyma. Curvilinear calcification (arrow) is seen. (b) Axial T1-weighted MR image shows isointensity within the mass, compared with the white matter. (c) Axial T2-weighted MR image shows heterogeneous hyperintensity within the mass and no evidence of periventricular edema. (d) Contrast-enhanced axial T1-weighted MR image shows scattered heterogeneous enhancement within the mass.

On MR images, subependymomas are generally hypointense compared with white matter with short TR pulse sequences and hyperintense compared with white matter with long TR pulse sequences (Figs 8 –10) (22–24). Heterogeneity is typical, with cystlike areas interspersed within the mass (22,24). When hemorrhage is present, characteristic signal intensity representative of hemoglobin by-products is noted (23). Enhancement is quite variable on contrast-enhanced images (22,23). They may not enhance, enhance minimally, or show intense enhancement after the intravenous administration of a contrast agent (24). Even when intense enhancement is seen, it is usually heterogeneous (2,24). Extension of a subependymoma beyond the ventricular margins is rare (23,27). These features may be helpful in distinguishing subependymomas from ependymomas, since the latter frequently have intense enhancement and extraventricular extension (24).

View larger version (182K): [in this window] [in a new window] [Download PPT slide]   Figure 9a.  Subependymoma in a 70-year-old woman in whom breast carcinoma had been diagnosed 7 years before. A metastatic lesion to the chest wall had been found 4 months before she experienced a sudden onset of weakness and slurred speech that prompted neuroimaging. (a) Sagittal T1-weighted MR image shows a mass that is isointense compared with the white matter and that extends inferiorly. A sellar mass of unknown pathologic characteristics erodes the floor of the sella turcica. (b) Axial T2-weighted MR image shows a fourth ventricular mass (arrows) that is slightly hyperintense compared with the white matter. A metastasis was suspected. (c) Intraoperative photograph shows the well-circumscribed, firm, glistening mass (arrows) in the inferior portion of the fourth ventricle. Findings from histologic examination confirmed subependymoma, not metastatic disease.

View larger version (179K): [in this window] [in a new window] [Download PPT slide]   Figure 9b.  Subependymoma in a 70-year-old woman in whom breast carcinoma had been diagnosed 7 years before. A metastatic lesion to the chest wall had been found 4 months before she experienced a sudden onset of weakness and slurred speech that prompted neuroimaging. (a) Sagittal T1-weighted MR image shows a mass that is isointense compared with the white matter and that extends inferiorly. A sellar mass of unknown pathologic characteristics erodes the floor of the sella turcica. (b) Axial T2-weighted MR image shows a fourth ventricular mass (arrows) that is slightly hyperintense compared with the white matter. A metastasis was suspected. (c) Intraoperative photograph shows the well-circumscribed, firm, glistening mass (arrows) in the inferior portion of the fourth ventricle. Findings from histologic examination confirmed subependymoma, not metastatic disease.

View larger version (117K): [in this window] [in a new window] [Download PPT slide]   Figure 9c.  Subependymoma in a 70-year-old woman in whom breast carcinoma had been diagnosed 7 years before. A metastatic lesion to the chest wall had been found 4 months before she experienced a sudden onset of weakness and slurred speech that prompted neuroimaging. (a) Sagittal T1-weighted MR image shows a mass that is isointense compared with the white matter and that extends inferiorly. A sellar mass of unknown pathologic characteristics erodes the floor of the sella turcica. (b) Axial T2-weighted MR image shows a fourth ventricular mass (arrows) that is slightly hyperintense compared with the white matter. A metastasis was suspected. (c) Intraoperative photograph shows the well-circumscribed, firm, glistening mass (arrows) in the inferior portion of the fourth ventricle. Findings from histologic examination confirmed subependymoma, not metastatic disease.

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.  Subependymoma in a 48-year-old man with a history of nausea for several months. Results from a prior abdominal CT study and endoscopy were negative. After developing new headaches, he presented again for evaluation. (a) Sagittal T1-weighted MR image shows a soft-tissue mass (arrows) in the inferior portion of the fourth ventricle with extension through the foramen magnum. Note dilatation of the remaining portions of the ventricular system as a result of the mass. (b) On an axial T2-weighted MR image, the mass appears heterogeneous, with cystic and soft-tissue components. Note absence of vasogenic edema. (c) Contrast-enhanced sagittal T1-weighted MR image shows intense heterogeneous enhancement of the mass.

View larger version (171K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.  Subependymoma in a 48-year-old man with a history of nausea for several months. Results from a prior abdominal CT study and endoscopy were negative. After developing new headaches, he presented again for evaluation. (a) Sagittal T1-weighted MR image shows a soft-tissue mass (arrows) in the inferior portion of the fourth ventricle with extension through the foramen magnum. Note dilatation of the remaining portions of the ventricular system as a result of the mass. (b) On an axial T2-weighted MR image, the mass appears heterogeneous, with cystic and soft-tissue components. Note absence of vasogenic edema. (c) Contrast-enhanced sagittal T1-weighted MR image shows intense heterogeneous enhancement of the mass.

View larger version (178K): [in this window] [in a new window] [Download PPT slide]   Figure 10c.  Subependymoma in a 48-year-old man with a history of nausea for several months. Results from a prior abdominal CT study and endoscopy were negative. After developing new headaches, he presented again for evaluation. (a) Sagittal T1-weighted MR image shows a soft-tissue mass (arrows) in the inferior portion of the fourth ventricle with extension through the foramen magnum. Note dilatation of the remaining portions of the ventricular system as a result of the mass. (b) On an axial T2-weighted MR image, the mass appears heterogeneous, with cystic and soft-tissue components. Note absence of vasogenic edema. (c) Contrast-enhanced sagittal T1-weighted MR image shows intense heterogeneous enhancement of the mass.

Central neurocytomas constitute approximately 0.25%–0.5% of all intracranial tumors (35). The mean age at presentation is 29 years, with a wide age range (8 days to 67 years) (29). Nearly half of all cases reported occur in the 3rd decade of life, and almost 75% of patients present between 20 and 40 years of age (29). There is no gender predilection (29). A relatively short clinical course (mean, 3 months) is typical, with the symptoms being related to increased intracranial pressure, mental status changes, visual deficits (secondary to papilledema), or hormonal changes (particularly for those lesions involving the third ventricle) (29,36,37). In rare cases, these tumors may be associated with sudden death secondary to acute ventricular obstruction (38). There is one case report of a central neurocytoma associated with gigantism, either from growth hormone– releasing factor within the tumor itself or from pressure on the hypothalamus (39).

Gross total surgical resection is the treatment of choice and typically curative (29). Recurrence of disease in patients who undergo such a procedure is uncommon (29). However, patients in whom operative limitations prevent a complete resection have an increased risk of recurrence and tend to have a less benign clinical course (29). In these cases, postoperative radiation therapy, chemotherapy, or stereotactic radiosurgery (gamma knife) may be used (40–42). A poorer clinical outcome is also usually seen in patients with central neurocytomas that undergo extraventricular extension (43,44).

Central neurocytomas arise from the septum pellucidum or the ventricular wall (40). Half of the cases involve the lateral ventricles near the foramen of Monro, whereas 15% are located in both the lateral and third ventricles (29). About 13% of central neurocytomas are bilateral, and only 3% occur in the third ventricle as an isolated location (29). There is a single case report of a central neurocytoma that arose in the fourth ventricle (45).

At gross inspection, central neurocytomas are typically gray and friable and often contain calcification or hemorrhage (29). They are considered WHO grade II tumors (29). The histologic features are so strikingly similar to those of an oligodendroglioma—with uniform round cells having round or oval nuclei (the classic "fried egg appearance"), as seen with the standard hematoxylin-eosin stain—that misdiagnosis of many central neurocytomas as intraventricular oligodendroglioma was common (Fig 11). The identification of pineocytomatous rosettes distinguishes these tumors from oligodendrogliomas in most cases. Calcification is very common (50% of specimens) (29). Central neurocytomas usually express immunoreactivity for synaptophysin and neuron-specific enolase, both markers for neuronal differentiation, which also aids in differentiating these tumors from oligodendrogliomas (29). In difficult cases, the final determination rests with electron microscopy, which depicts finely speckled chromatin, a small distinct nucleolus, and cell processes exhibiting typical neuritic features including microtubules (29).

View larger version (219K): [in this window] [in a new window] [Download PPT slide]   Figure 11.  Central neurocytoma. Photomicrograph (original magnification, x400; hematoxylin-eosin stain) of a central neurocytoma shows sheets of neoplastic cells with round, regular nuclei.

The histogenesis of central neurocytomas remains unclear. Although the immunohistochemical features support a neuronal lineage, there are recent cell-culture investigations that indicate that the tumors may be derived from bipotential progenitor cells that are capable of both neuronal and glial differentiation (29,48). These cells may be located in the subependymal plate, which would provide a possible explanation for why some neurocytomas are extraventricular (48). Because both cell lines may be involved in neurocytomas, they are considered neuroepithelial tumors (29,48).

The typical cross-sectional imaging appearance of a central neurocytoma is a well-circumscribed, heavily lobulated, intraventricular mass with numerous intratumoral cystlike areas (Figs 12, 13) (43). The mass is most commonly located in the lateral ventricle, usually in its anterior portion near the foramen of Monro. Accordingly, a solid majority of cases of central neurocytoma are affiliated with hydrocephalus or monoventricular dilatation (49). On CT images, the lesions are hyperattenuated compared with the brain parenchyma (43,50). Cystlike areas are noted in two-thirds of cases with imaging studies (43). Calcification, usually punctate in character, is present in half of the cases (36,43). Moderate enhancement is typical after the intravenous administration of contrast media on both CT and MR images (43).

View larger version (128K): [in this window] [in a new window] [Download PPT slide]   Figure 12a.  Central neurocytoma. (a) Axial CT image shows a hyperattenuated mass with focal calcification (arrowhead) centered near the foramen of Monro. (b) Axial T1-weighted MR image shows mild heterogeneity within the mass. The septum pellucidum is displaced toward the contralateral side, and the ipsilateral ventricle is clearly enlarged. (c) On a coronal T2-weighted MR image, the mass has an even more heterogeneous appearance. (d) Contrast-enhanced coronal T1-weighted MR image shows patchy enhancement within the mass. (e) Intraoperative photograph shows the soft-tissue mass at the depths of the retractors (r).

View larger version (135K): [in this window] [in a new window] [Download PPT slide]   Figure 12b.  Central neurocytoma. (a) Axial CT image shows a hyperattenuated mass with focal calcification (arrowhead) centered near the foramen of Monro. (b) Axial T1-weighted MR image shows mild heterogeneity within the mass. The septum pellucidum is displaced toward the contralateral side, and the ipsilateral ventricle is clearly enlarged. (c) On a coronal T2-weighted MR image, the mass has an even more heterogeneous appearance. (d) Contrast-enhanced coronal T1-weighted MR image shows patchy enhancement within the mass. (e) Intraoperative photograph shows the soft-tissue mass at the depths of the retractors (r).

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 12c.  Central neurocytoma. (a) Axial CT image shows a hyperattenuated mass with focal calcification (arrowhead) centered near the foramen of Monro. (b) Axial T1-weighted MR image shows mild heterogeneity within the mass. The septum pellucidum is displaced toward the contralateral side, and the ipsilateral ventricle is clearly enlarged. (c) On a coronal T2-weighted MR image, the mass has an even more heterogeneous appearance. (d) Contrast-enhanced coronal T1-weighted MR image shows patchy enhancement within the mass. (e) Intraoperative photograph shows the soft-tissue mass at the depths of the retractors (r).

View larger version (149K): [in this window] [in a new window] [Download PPT slide]   Figure 12d.  Central neurocytoma. (a) Axial CT image shows a hyperattenuated mass with focal calcification (arrowhead) centered near the foramen of Monro. (b) Axial T1-weighted MR image shows mild heterogeneity within the mass. The septum pellucidum is displaced toward the contralateral side, and the ipsilateral ventricle is clearly enlarged. (c) On a coronal T2-weighted MR image, the mass has an even more heterogeneous appearance. (d) Contrast-enhanced coronal T1-weighted MR image shows patchy enhancement within the mass. (e) Intraoperative photograph shows the soft-tissue mass at the depths of the retractors (r).

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 12e.  Central neurocytoma. (a) Axial CT image shows a hyperattenuated mass with focal calcification (arrowhead) centered near the foramen of Monro. (b) Axial T1-weighted MR image shows mild heterogeneity within the mass. The septum pellucidum is displaced toward the contralateral side, and the ipsilateral ventricle is clearly enlarged. (c) On a coronal T2-weighted MR image, the mass has an even more heterogeneous appearance. (d) Contrast-enhanced coronal T1-weighted MR image shows patchy enhancement within the mass. (e) Intraoperative photograph shows the soft-tissue mass at the depths of the retractors (r).

View larger version (156K): [in this window] [in a new window] [Download PPT slide]   Figure 13a.  Central neurocytoma. (a) Axial CT image shows a heterogeneous, hyperattenuated mass in the right lateral ventricle. Note the asymmetry of the lateral ventricles secondary to obstruction of CSF flow from the right lateral ventricle. (b) Coronal view from cerebral angiography following a right internal carotid artery injection shows a subtle blush (arrows) in the region of the right lateral ventricle. (c) Lateral view from the same study shows a similar blush (arrows).

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 13b.  Central neurocytoma. (a) Axial CT image shows a heterogeneous, hyperattenuated mass in the right lateral ventricle. Note the asymmetry of the lateral ventricles secondary to obstruction of CSF flow from the right lateral ventricle. (b) Coronal view from cerebral angiography following a right internal carotid artery injection shows a subtle blush (arrows) in the region of the right lateral ventricle. (c) Lateral view from the same study shows a similar blush (arrows).

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 13c.  Central neurocytoma. (a) Axial CT image shows a heterogeneous, hyperattenuated mass in the right lateral ventricle. Note the asymmetry of the lateral ventricles secondary to obstruction of CSF flow from the right lateral ventricle. (b) Coronal view from cerebral angiography following a right internal carotid artery injection shows a subtle blush (arrows) in the region of the right lateral ventricle. (c) Lateral view from the same study shows a similar blush (arrows).

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 14a.  Central neurocytoma in a 46-year-old man with mood changes, lethargy, and recent onset of right-sided weakness. (a) Axial T1-weighted MR image shows a mass entrapping the left lateral ventricle. Notice the different signal intensity (arrowhead) within the left lateral ventricle compared with the right side. The mass is mildly hypointense compared with the white matter but is heterogeneous with scattered focal areas of mild hyperintense signal. (b) Axial T2-weighted MR image shows the heterogeneous mass with numerous cystlike areas and vasogenic edema (arrows) in the adjacent centrum semiovale. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of most of the mass, with sparing of the cystlike regions. At surgery, the tumor was difficult to resect because of invasion into the adjacent brain parenchyma.

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 14b.  Central neurocytoma in a 46-year-old man with mood changes, lethargy, and recent onset of right-sided weakness. (a) Axial T1-weighted MR image shows a mass entrapping the left lateral ventricle. Notice the different signal intensity (arrowhead) within the left lateral ventricle compared with the right side. The mass is mildly hypointense compared with the white matter but is heterogeneous with scattered focal areas of mild hyperintense signal. (b) Axial T2-weighted MR image shows the heterogeneous mass with numerous cystlike areas and vasogenic edema (arrows) in the adjacent centrum semiovale. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of most of the mass, with sparing of the cystlike regions. At surgery, the tumor was difficult to resect because of invasion into the adjacent brain parenchyma.

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 14c.  Central neurocytoma in a 46-year-old man with mood changes, lethargy, and recent onset of right-sided weakness. (a) Axial T1-weighted MR image shows a mass entrapping the left lateral ventricle. Notice the different signal intensity (arrowhead) within the left lateral ventricle compared with the right side. The mass is mildly hypointense compared with the white matter but is heterogeneous with scattered focal areas of mild hyperintense signal. (b) Axial T2-weighted MR image shows the heterogeneous mass with numerous cystlike areas and vasogenic edema (arrows) in the adjacent centrum semiovale. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of most of the mass, with sparing of the cystlike regions. At surgery, the tumor was difficult to resect because of invasion into the adjacent brain parenchyma.

Subependymal Giant Cell Astrocytoma
SEGA is the most common cerebral neoplasm in tuberous sclerosis, the neurocutaneous phakomatosis characterized by an autosomal dominant pattern of inheritance in 20%–50% of cases and the presence of tubers and subependymal glial nodules in 90%–100% of patients (57–59). Still, the SEGA is an uncommon tumor, accounting for only 1.4% of 733 pediatric brain neoplasms in one series (60).

There is a wide age range for presentation (birth to the 5th decade of life), but most cases occur in the 1st and 2nd decades, with a mean age of 11 years (combining data from the two largest series reported) (57,58,60–62). Among all patients with tuberous sclerosis, about 6%–16% have a SEGA (58). Whether a SEGA can occur in patients who do not harbor any manifestations of tuberous sclerosis is controversial. Although there have been patients who have a SEGA without manifestations of tuberous sclerosis, the apparent absence of tuberous sclerosis may simply be a reflection of an insufficient period of time having elapsed before the clinical signs could be documented or an example of variable gene expression (57,60).

Because the tumor is virtually always located near the foramen of Monro, symptoms related to increased intracranial pressure and seizures are the typical clinical manifestations (58). Hemiparesis has also been reported (60). Since most patients do not have a change in their seizure pattern after removal of a SEGA, it is doubtful that the SEGA caused the seizures; rather, they are more likely secondary to the usually numerous other intracranial tubers and nodules present in a patient with tuberous sclerosis (60). Menor et al (59) noted a higher rate of prevalence (80%) of cardiac rhabdomyomas in their five patients with SEGA, compared with the other 22 tuberous sclerosis patients without a SEGA.

The tumor is characterized by slow growth and a benign biologic behavior, corresponding to WHO grade I in the latest WHO classification scheme (58). In a series of 21 patients with SEGA, earlier diagnosis was associated with increased survival (57).

Current neurosurgical opinion supports resection of a symptomatic SEGA or a SEGA with documented growth on MR images (60). The development of better neurosurgical techniques has led to decreased perioperative mortality and morbidity in the resection of these lesions (60). Recurrence after surgical removal is rare (60). Radiation therapy has not been effective in preventing growth of SEGAs (60).

SEGAs probably arise from subependymal nodules in the ventricular wall of patients with tuberous sclerosis (57). Why an otherwise unremarkable subependymal nodule in a tuberous sclerosis patient would transform into a SEGA is still a mystery, as is the natural history of this tumor (57). The histogenesis of SEGA is also unclear, with evidence supporting both neuronal and astrocytic lineage (57). SEGA is histologically characterized by a mixed glioneuronal pattern and has a low proliferative index, corresponding to its slow growth (Fig 15) (58). Malignant histologic features in a SEGA are rare (57).

View larger version (197K): [in this window] [in a new window] [Download PPT slide]   Figure 15.  Subependymal giant cell astrocytoma. Photomicrograph (original magnification, x200; hematoxylin-eosin stain) of a SEGA shows collections of large, bizarre cells (arrowheads) in a glial background.

View larger version (169K): [in this window] [in a new window] [Download PPT slide]   Figure 16a.  SEGA in a 23-year-old man with occipital headache, lethargy, nausea, vomiting. (a) Axial CT image shows an intraventricular mass (arrow) near the foramen of Monro. Focal calcification (arrowhead) is seen. (b) Axial CT image obtained at a different level than a shows several calcified subependymal nodules along the lateral ventricle surface. (c) On an axial T1-weighted MR image, the mass is heterogeneous and slightly hypointense compared with the white matter. (d) On an axial T2-weighted MR image, the mass has heterogeneous hyperintensity compared with the white matter. (e) Contrast-enhanced axial T1-weighted MR image shows intense homogeneous enhancement of the mass.

View larger version (172K): [in this window] [in a new window] [Download PPT slide]   Figure 16b.  SEGA in a 23-year-old man with occipital headache, lethargy, nausea, vomiting. (a) Axial CT image shows an intraventricular mass (arrow) near the foramen of Monro. Focal calcification (arrowhead) is seen. (b) Axial CT image obtained at a different level than a shows several calcified subependymal nodules along the lateral ventricle surface. (c) On an axial T1-weighted MR image, the mass is heterogeneous and slightly hypointense compared with the white matter. (d) On an axial T2-weighted MR image, the mass has heterogeneous hyperintensity compared with the white matter. (e) Contrast-enhanced axial T1-weighted MR image shows intense homogeneous enhancement of the mass.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 16c.  SEGA in a 23-year-old man with occipital headache, lethargy, nausea, vomiting. (a) Axial CT image shows an intraventricular mass (arrow) near the foramen of Monro. Focal calcification (arrowhead) is seen. (b) Axial CT image obtained at a different level than a shows several calcified subependymal nodules along the lateral ventricle surface. (c) On an axial T1-weighted MR image, the mass is heterogeneous and slightly hypointense compared with the white matter. (d) On an axial T2-weighted MR image, the mass has heterogeneous hyperintensity compared with the white matter. (e) Contrast-enhanced axial T1-weighted MR image shows intense homogeneous enhancement of the mass.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 16d.  SEGA in a 23-year-old man with occipital headache, lethargy, nausea, vomiting. (a) Axial CT image shows an intraventricular mass (arrow) near the foramen of Monro. Focal calcification (arrowhead) is seen. (b) Axial CT image obtained at a different level than a shows several calcified subependymal nodules along the lateral ventricle surface. (c) On an axial T1-weighted MR image, the mass is heterogeneous and slightly hypointense compared with the white matter. (d) On an axial T2-weighted MR image, the mass has heterogeneous hyperintensity compared with the white matter. (e) Contrast-enhanced axial T1-weighted MR image shows intense homogeneous enhancement of the mass.

View larger version (138K): [in this window] [in a new window] [Download PPT slide]   Figure 16e.  SEGA in a 23-year-old man with occipital headache, lethargy, nausea, vomiting. (a) Axial CT image shows an intraventricular mass (arrow) near the foramen of Monro. Focal calcification (arrowhead) is seen. (b) Axial CT image obtained at a different level than a shows several calcified subependymal nodules along the lateral ventricle surface. (c) On an axial T1-weighted MR image, the mass is heterogeneous and slightly hypointense compared with the white matter. (d) On an axial T2-weighted MR image, the mass has heterogeneous hyperintensity compared with the white matter. (e) Contrast-enhanced axial T1-weighted MR image shows intense homogeneous enhancement of the mass.

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 17a.  SEGA in a 16-year-old boy with a long history of adenoma sebaceum, seizures, and psychomotor developmental delay. (a) Axial T1-weighted MR image shows bilateral masses (arrows) near the foramen of Monro. The masses are slightly hypointense compared with the white matter. (b) On an axial T2-weighted MR image, the masses are slightly hyperintense compared with the white matter. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of both masses.

View larger version (182K): [in this window] [in a new window] [Download PPT slide]   Figure 17b.  SEGA in a 16-year-old boy with a long history of adenoma sebaceum, seizures, and psychomotor developmental delay. (a) Axial T1-weighted MR image shows bilateral masses (arrows) near the foramen of Monro. The masses are slightly hypointense compared with the white matter. (b) On an axial T2-weighted MR image, the masses are slightly hyperintense compared with the white matter. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of both masses.

View larger version (154K): [in this window] [in a new window] [Download PPT slide]   Figure 17c.  SEGA in a 16-year-old boy with a long history of adenoma sebaceum, seizures, and psychomotor developmental delay. (a) Axial T1-weighted MR image shows bilateral masses (arrows) near the foramen of Monro. The masses are slightly hypointense compared with the white matter. (b) On an axial T2-weighted MR image, the masses are slightly hyperintense compared with the white matter. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of both masses.

	Neoplasms of the Choroid Plexus

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Neoplasms of the Ventricular... Neoplasms of the Choroid... Summary References

Neoplasms of the choroid plexus arise anywhere this tissue exists. Based on the amount of choroidal tissue present, it is not surprising that the lateral ventricle is the most common site (50% of cases) for these tumors, followed by the fourth ventricle (40%) and the third ventricle (5%) (67). About 5% of choroid plexus tumors are in more than one location (67). There are rare case reports of choroid plexus tumors arising in extraventricular locations, including the cerebellopontine angle, the suprasellar region, the frontal lobe, the posterior commissure, the pineal gland, and the cerebellum (68–75). An embryonic rest of choroid plexus is speculated as the cause of these extraventricular lesions, but the theory remains unproved (68).

Neoplasms of the choroid plexus account for 0.4%–0.6% of all intracranial tumors, 2%–4% of pediatric brain tumors, and 10%–20% of brain tumors in children younger than 1 year of age (67). Nearly half of these tumors manifest in the 1st decade of life (76). Most choroid plexus tumors (about 80%) occur as the benign, slowly growing choroid plexus papilloma, a WHO grade I tumor with a favorable overall prognosis (67). The other 20% of cases manifest as a much more biologically aggressive WHO grade III tumor, the choroid plexus carcinoma, which is far more common in children than adults (67). The overall prevalence of both types of choroid plexus tumors is about 0.3 per 1 million (67).

The typical age at presentation varies with the location of the tumor. Tumors that arise in the lateral ventricle are much more common in patients 10 years of age or less, whereas those that arise in the fourth ventricle are fairly evenly distributed among patients 0–50 years of age (67). There is no gender predilection for lateral ventricular tumors, whereas those that occur in the fourth ventricle are more commonly found in males (67).

Choroid plexus tumors have long been associated with hydrocephalus and symptoms related to increased intracranial pressure (77–79). In most cases, the increased intraventricular pressure is secondary to an increase in the production of CSF by the tumor (78). It is well documented that choroid plexus tumors may produce CSF in amounts far exceeding the average of 450 mL per day that is normally observed (79). Simple obstruction of CSF flow from large or well-placed intraventricular masses is also a contributing factor in some cases (80). In addition, the facts that some patients require postoperative shunting to treat persistent hydrocephalus and that some have xanthochromic CSF indicative of subclinical bleeding support the contention that impaired CSF absorption at the level of the arachnoid granulations (secondary to hemorrhage or proteinaceous material from these highly vascular tumors) may also be a factor (79). Unfortunately, no preoperative findings have been identified that reliably predict the onset of postoperative hydrocephalus (79).

Other clinical findings include focal neurologic deficits, cranial nerve palsies, seizures, coma, and even psychosis in one case report (77,81). A small number of cases of choroid plexus tumors have occurred in patients with Li-Fraumeni syndrome and Aicardi syndrome; thus, choroid plexus tumors join a long list of other cerebral neoplasms that are associated with both of these phenomena (82–84).

Since the first surgical attempt at removal of a choroid plexus tumor in 1902, most early attempts to safely resect these tumors surgically were unsuccessful and the mortality rate for these procedures was exceedingly high (78,85). With improvements in surgical techniques, especially in securing the vascular supply to these tumors (by surgical ligation of the vascular pedicle or by preoperative embolization), the mortality rate for the surgical resection of these lesions has dropped substantially in recent years (76,86). Today, the prognosis for patients with choroid plexus papilloma is excellent, with a report of 100% survival at 5 years after surgical resection in one large series, and adjuvant therapy is not indicated in these patients (76,79). Unfortunately, the prognosis for patients with choroid plexus carcinoma is guarded, with an overall 5-year survival rate of 26%–50% (77,79,87). The presence of residual disease on postoperative images is an especially poor prognostic factor (87). Radiation therapy is often not an option as adjuvant therapy in these patients because of their young age (79). Chemotherapy may prolong survival but has not proved efficacious in eliminating the risk of recurrent disease (79).

Choroid plexus tumors are soft well-circumscribed cauliflower-like masses with prominent lobulations peripherally (67,76). Hemorrhage and cyst formation may be seen (67). Necrosis and parenchymal invasion are characteristic features for choroid plexus carcinoma (67). Many choroid plexus tumors are attached by a vascular pedicle to the choroid plexus. Those arising in the lateral ventricle are usually attached to the choroid plexus in the trigone region, whereas those located in the third ventricle have their attachment to its roof and fourth ventricular tumors are attached to the posterior medullary velum (80). Those tumors that have a pedicular attachment may move within the ventricle, giving rise to acute gravity-dependent intermittent ventricular obstruction, and have been associated with the bobble-head doll syndrome in some cases (80,88).

Histologic examination of choroid plexus papillomas reveals an appearance quite similar to that of normal nonneoplastic choroid plexus tissue (67). Prominent fronds of fibrovascular connective tissue surrounded by columnar or cuboidal cells without significant mitotic activity are typical (Fig 18) (67). In contrast, the choroid plexus carcinoma demonstrates clear signs of malignancy, with hypercellularity, nuclear pleomorphism, high nucleus-cytoplasm ratio, conspicuous mitotic activity, and invasion into the adjacent brain parenchyma (Fig 19) (67). Although the vast majority of choroid plexus tumors are clearly categorized as a papilloma or carcinoma, occasionally a tumor with a predominantly papilloma appearance may have one or two malignant features. These findings are not sufficient by themselves to establish the tumor as a carcinoma, and, in this setting, the term atypical choroid plexus papilloma is used (67). Transformation from a choroid plexus papilloma to a choroid plexus carcinoma has been reported in a small number of cases (89).

View larger version (176K): [in this window] [in a new window] [Download PPT slide]   Figure 18.  Choroid plexus papilloma. Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a choroid plexus papilloma shows a distinctive papillary pattern, with bland columnar to cuboidal cells lining fibrovascular stalks.

View larger version (169K): [in this window] [in a new window] [Download PPT slide]   Figure 19.  Choroid plexus carcinoma. Photomicrograph (original magnification, x200; hematoxylin-eosin stain) of a choroid plexus carcinoma shows a solid growth of markedly pleomorphic cells with loss of any papillary growth pattern.

Choroid plexus tumors are generally isoattenuated to hyperattenuated intraventricular masses without brain invasion on nonenhanced CT images and show intense enhancement on contrast-enhanced images (Fig 20) (79,80). Hydrocephalus is very common (79). When these tumors occur in the region of the trigone, engulfment rather than invasion of the choroid plexus glomus has been described as a means to differentiate choroid plexus tumors from other lesions (94). Calcification is noted in 4%–10% of choroid plexus tumors on plain skull radiographs and in 24% on CT images (70,79,95). The degree of calcification varies widely, from scattered punctate foci to calcification involving the entire mass (96). Extension from one ventricle to another or into the cerebellopontine angle is a characteristic feature of choroid plexus tumors (97). Erosion of the petrous bone has been described in a choroid plexus papilloma arising in the cerebellopontine angle (69). Early reports of a predilection for the left lateral ventricle have not been substantiated in more recent studies (80,86).

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 20a.  Choroid plexus papilloma in a 34-year-old man with a history of hand tremor for 10 years and a more recent history of delayed slow speech and apathetic state. (a) Axial CT image shows a heterogeneous, partially calcified, soft-tissue mass within the fourth ventricle. (b) Coronal T1-weighted MR image shows the heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted MR image, the mass is heterogeneously hyperintense compared with the cerebellum. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense, near homogeneous enhancement. (e) Intraoperative photograph shows the lobulated vascular mass. Findings from the histologic examination confirmed a choroid plexus papilloma.

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 20b.  Choroid plexus papilloma in a 34-year-old man with a history of hand tremor for 10 years and a more recent history of delayed slow speech and apathetic state. (a) Axial CT image shows a heterogeneous, partially calcified, soft-tissue mass within the fourth ventricle. (b) Coronal T1-weighted MR image shows the heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted MR image, the mass is heterogeneously hyperintense compared with the cerebellum. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense, near homogeneous enhancement. (e) Intraoperative photograph shows the lobulated vascular mass. Findings from the histologic examination confirmed a choroid plexus papilloma.

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 20c.  Choroid plexus papilloma in a 34-year-old man with a history of hand tremor for 10 years and a more recent history of delayed slow speech and apathetic state. (a) Axial CT image shows a heterogeneous, partially calcified, soft-tissue mass within the fourth ventricle. (b) Coronal T1-weighted MR image shows the heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted MR image, the mass is heterogeneously hyperintense compared with the cerebellum. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense, near homogeneous enhancement. (e) Intraoperative photograph shows the lobulated vascular mass. Findings from the histologic examination confirmed a choroid plexus papilloma.

View larger version (150K): [in this window] [in a new window] [Download PPT slide]   Figure 20d.  Choroid plexus papilloma in a 34-year-old man with a history of hand tremor for 10 years and a more recent history of delayed slow speech and apathetic state. (a) Axial CT image shows a heterogeneous, partially calcified, soft-tissue mass within the fourth ventricle. (b) Coronal T1-weighted MR image shows the heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted MR image, the mass is heterogeneously hyperintense compared with the cerebellum. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense, near homogeneous enhancement. (e) Intraoperative photograph shows the lobulated vascular mass. Findings from the histologic examination confirmed a choroid plexus papilloma.

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 20e.  Choroid plexus papilloma in a 34-year-old man with a history of hand tremor for 10 years and a more recent history of delayed slow speech and apathetic state. (a) Axial CT image shows a heterogeneous, partially calcified, soft-tissue mass within the fourth ventricle. (b) Coronal T1-weighted MR image shows the heterogeneous mass, which is slightly hypointense compared with the cerebellum. (c) On an axial T2-weighted MR image, the mass is heterogeneously hyperintense compared with the cerebellum. (d) On a contrast-enhanced axial T1-weighted MR image, the mass shows intense, near homogeneous enhancement. (e) Intraoperative photograph shows the lobulated vascular mass. Findings from the histologic examination confirmed a choroid plexus papilloma.

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 21a.  Choroid plexus papilloma. (a) Axial T1-weighted MR image shows a large, lobulated mass centered in the region of the choroid plexus glomus of the left lateral ventricle. There is also entrapment of the posterior portion of this ventricle by the mass. (b) Axial T2-weighted MR image shows marked hypointensity within the mass. (c) Contrast-enhanced axial T1-weighted MR image shows intense homogeneous enhancement of the mass.

View larger version (161K): [in this window] [in a new window] [Download PPT slide]   Figure 21b.  Choroid plexus papilloma. (a) Axial T1-weighted MR image shows a large, lobulated mass centered in the region of the choroid plexus glomus of the left lateral ventricle. There is also entrapment of the posterior portion of this ventricle by the mass. (b) Axial T2-weighted MR image shows marked hypointensity within the mass. (c) Contrast-enhanced axial T1-weighted MR image shows intense homogeneous enhancement of the mass.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 21c.  Choroid plexus papilloma. (a) Axial T1-weighted MR image shows a large, lobulated mass centered in the region of the choroid plexus glomus of the left lateral ventricle. There is also entrapment of the posterior portion of this ventricle by the mass. (b) Axial T2-weighted MR image shows marked hypointensity within the mass. (c) Contrast-enhanced axial T1-weighted MR image shows intense homogeneous enhancement of the mass.

Choroid plexus carcinomas tend to be more heterogeneous than choroid plexus papillomas on CT and MR images, reflecting the presence of more necrosis and parenchymal invasion in the more malignant tumor (Figs 22, 23). The findings of extraventricular extension of a choroid plexus tumor into the brain parenchyma, heterogeneity of signal intensity, and the presence of vasogenic edema in the cerebral white matter all favor the imaging diagnosis of a choroid plexus carcinoma (80). The degree of hydrocephalus in choroid plexus carcinomas has also been noted to be less than that seen in choroid plexus papillomas (80). However, there is considerable overlap in the imaging appearances of papillomas and carcinomas, and the distinction between the two neoplasms is not always well-defined on imaging studies (96,101). Increased metabolic activity consistent with increased glycolysis has been seen in a choroid plexus carcinoma at fluorine-18 fluorodeoxyglucose PET (102).

View larger version (172K): [in this window] [in a new window] [Download PPT slide]   Figure 22a.  Choroid plexus carcinoma. (a) Axial CT image shows a lobulated, hyperattenuated, intraventricular mass within the posterior portion of the lateral ventricle. There is surrounding vasogenic edema (arrows). (b) Axial T1-weighted MR image shows the lobulated mass with heterogeneous signal intensity. (c) On an axial T2-weighted MR image, the mass is slightly hyperintense compared with the white matter. The vasogenic edema is more conspicuous than in a. Circumferential marked hypointensity (arrowheads) suggests hemosiderin deposition. (d) Contrast-enhanced axial T1-weighted MR image shows intense but heterogeneous enhancement within the mass. At surgery, the ventricular wall was transgressed by the mass, and histologic analysis confirmed choroid plexus carcinoma.

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 22b.  Choroid plexus carcinoma. (a) Axial CT image shows a lobulated, hyperattenuated, intraventricular mass within the posterior portion of the lateral ventricle. There is surrounding vasogenic edema (arrows). (b) Axial T1-weighted MR image shows the lobulated mass with heterogeneous signal intensity. (c) On an axial T2-weighted MR image, the mass is slightly hyperintense compared with the white matter. The vasogenic edema is more conspicuous than in a. Circumferential marked hypointensity (arrowheads) suggests hemosiderin deposition. (d) Contrast-enhanced axial T1-weighted MR image shows intense but heterogeneous enhancement within the mass. At surgery, the ventricular wall was transgressed by the mass, and histologic analysis confirmed choroid plexus carcinoma.

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 22c.  Choroid plexus carcinoma. (a) Axial CT image shows a lobulated, hyperattenuated, intraventricular mass within the posterior portion of the lateral ventricle. There is surrounding vasogenic edema (arrows). (b) Axial T1-weighted MR image shows the lobulated mass with heterogeneous signal intensity. (c) On an axial T2-weighted MR image, the mass is slightly hyperintense compared with the white matter. The vasogenic edema is more conspicuous than in a. Circumferential marked hypointensity (arrowheads) suggests hemosiderin deposition. (d) Contrast-enhanced axial T1-weighted MR image shows intense but heterogeneous enhancement within the mass. At surgery, the ventricular wall was transgressed by the mass, and histologic analysis confirmed choroid plexus carcinoma.

View larger version (170K): [in this window] [in a new window] [Download PPT slide]   Figure 22d.  Choroid plexus carcinoma. (a) Axial CT image shows a lobulated, hyperattenuated, intraventricular mass within the posterior portion of the lateral ventricle. There is surrounding vasogenic edema (arrows). (b) Axial T1-weighted MR image shows the lobulated mass with heterogeneous signal intensity. (c) On an axial T2-weighted MR image, the mass is slightly hyperintense compared with the white matter. The vasogenic edema is more conspicuous than in a. Circumferential marked hypointensity (arrowheads) suggests hemosiderin deposition. (d) Contrast-enhanced axial T1-weighted MR image shows intense but heterogeneous enhancement within the mass. At surgery, the ventricular wall was transgressed by the mass, and histologic analysis confirmed choroid plexus carcinoma.

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 23a.  Choroid plexus carcinoma. (a) Sagittal T1-weighted MR image shows a huge lobulated lateral ventricular mass with prominent flow voids (arrowheads). (b) Axial T2-weighted MR image shows heterogeneity within the mass and surrounding vasogenic edema (arrows). (c) Contrast-enhanced sagittal T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced axial T1-weighted MR image shows bilateral masses. (e) MR spectroscopy shows increased levels of choline (Cho) with a decreased amount of N-acetylaspartate (NAA), and a mildly elevated peak of lactate (Lac). These features favor a malignant neoplasm. Peak at 3.6 ppm is likely secondary to inositol (Ino).

View larger version (144K): [in this window] [in a new window] [Download PPT slide]   Figure 23b.  Choroid plexus carcinoma. (a) Sagittal T1-weighted MR image shows a huge lobulated lateral ventricular mass with prominent flow voids (arrowheads). (b) Axial T2-weighted MR image shows heterogeneity within the mass and surrounding vasogenic edema (arrows). (c) Contrast-enhanced sagittal T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced axial T1-weighted MR image shows bilateral masses. (e) MR spectroscopy shows increased levels of choline (Cho) with a decreased amount of N-acetylaspartate (NAA), and a mildly elevated peak of lactate (Lac). These features favor a malignant neoplasm. Peak at 3.6 ppm is likely secondary to inositol (Ino).

View larger version (141K): [in this window] [in a new window] [Download PPT slide]   Figure 23c.  Choroid plexus carcinoma. (a) Sagittal T1-weighted MR image shows a huge lobulated lateral ventricular mass with prominent flow voids (arrowheads). (b) Axial T2-weighted MR image shows heterogeneity within the mass and surrounding vasogenic edema (arrows). (c) Contrast-enhanced sagittal T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced axial T1-weighted MR image shows bilateral masses. (e) MR spectroscopy shows increased levels of choline (Cho) with a decreased amount of N-acetylaspartate (NAA), and a mildly elevated peak of lactate (Lac). These features favor a malignant neoplasm. Peak at 3.6 ppm is likely secondary to inositol (Ino).

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 23d.  Choroid plexus carcinoma. (a) Sagittal T1-weighted MR image shows a huge lobulated lateral ventricular mass with prominent flow voids (arrowheads). (b) Axial T2-weighted MR image shows heterogeneity within the mass and surrounding vasogenic edema (arrows). (c) Contrast-enhanced sagittal T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced axial T1-weighted MR image shows bilateral masses. (e) MR spectroscopy shows increased levels of choline (Cho) with a decreased amount of N-acetylaspartate (NAA), and a mildly elevated peak of lactate (Lac). These features favor a malignant neoplasm. Peak at 3.6 ppm is likely secondary to inositol (Ino).

View larger version (38K): [in this window] [in a new window] [Download PPT slide]   Figure 23e.  Choroid plexus carcinoma. (a) Sagittal T1-weighted MR image shows a huge lobulated lateral ventricular mass with prominent flow voids (arrowheads). (b) Axial T2-weighted MR image shows heterogeneity within the mass and surrounding vasogenic edema (arrows). (c) Contrast-enhanced sagittal T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced axial T1-weighted MR image shows bilateral masses. (e) MR spectroscopy shows increased levels of choline (Cho) with a decreased amount of N-acetylaspartate (NAA), and a mildly elevated peak of lactate (Lac). These features favor a malignant neoplasm. Peak at 3.6 ppm is likely secondary to inositol (Ino).

Meningioma
Intraventricular meningiomas are rare, constituting only 0.7% of all meningiomas (104). Still, this tumor is one of the more common intraventricular neoplasms in the adult population, and, in some reports, a meningioma is the most common atrial mass to manifest in an adult patient (105–107). Most intraventricular meningiomas occur in patients older than 30 years, with the peak agebeing between 30 and 60 years (mean, 42 years) (105,108). Females are more likely to be affected by a 2:1 ratio (105). In the pediatric population, almost one-fifth of all meningiomas occur within the ventricular system (109). Patients with intraventricular meningiomas present with symptoms related to increased intracranial pressure (headache, nausea, vomiting), contralateral sensory or motor deficits, and homonymous hemianopsia (108).

Intraventricular meningiomas are believed to arise from the arachnoidal cap cells trapped within the choroid plexus, the tela choroidea, or the velum interpositum (104,109). Correspondingly, the trigone of the lateral ventricle is the most common site, with a slight majority of the reported cases being located on the left side (104,105,109). Less commonly, they may arise within the third ventricle or, very rarely, in the fourth ventricle (110). Nearly all of these tumors have benign histologic characteristics. However, meningiomas that arise within the ventricles of children have an increased predilection for sarcomatous changes (109). Metastasis from an intraventricular location is rare (111,112).

On CT images, intraventricular meningiomas manifest with an appearance similar to that of other intracranial meningiomas: a well-defined globular mass that demonstrates hyperattenuation compared with the brain parenchyma (Fig 24) (113). Local or diffuse ventricular dilatation is present, depending on the degree of obstruction of CSF egress through the ventricular system. Calcification is common (50% of cases), and periventricular edema, presumably from reversal of transependymal CSF flow, may also be seen (105,113,114). In rare cases, subarachnoid hemorrhage or intraventricular hemorrhage may be seen (105).

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 24a.  Intraventricular meningioma. (a) Axial CT image shows a heterogeneous, lobulated mass arising in the atrium of the left lateral ventricle. Subtle region of mild hyperattenuation (arrowhead) is noted along the anteromedial margin of the mass. (b) On an axial T1-weighted MR image, the mass is isointense relative to gray matter. Focal area of hyperintensity (arrowhead) correlates with the same area seen in a and suggests hemorrhage or calcification. (c) On an axial T2-weighted MR image, the mass shows even more heterogeneity, with prominent peripheral areas of marked hypointensity suggestive of deposition of hemosiderin (small arrows). Vasogenic edema (large arrows) is present in the surrounding brain parenchyma. (d) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass.

View larger version (133K): [in this window] [in a new window] [Download PPT slide]   Figure 24b.  Intraventricular meningioma. (a) Axial CT image shows a heterogeneous, lobulated mass arising in the atrium of the left lateral ventricle. Subtle region of mild hyperattenuation (arrowhead) is noted along the anteromedial margin of the mass. (b) On an axial T1-weighted MR image, the mass is isointense relative to gray matter. Focal area of hyperintensity (arrowhead) correlates with the same area seen in a and suggests hemorrhage or calcification. (c) On an axial T2-weighted MR image, the mass shows even more heterogeneity, with prominent peripheral areas of marked hypointensity suggestive of deposition of hemosiderin (small arrows). Vasogenic edema (large arrows) is present in the surrounding brain parenchyma. (d) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass.

View larger version (148K): [in this window] [in a new window] [Download PPT slide]   Figure 24c.  Intraventricular meningioma. (a) Axial CT image shows a heterogeneous, lobulated mass arising in the atrium of the left lateral ventricle. Subtle region of mild hyperattenuation (arrowhead) is noted along the anteromedial margin of the mass. (b) On an axial T1-weighted MR image, the mass is isointense relative to gray matter. Focal area of hyperintensity (arrowhead) correlates with the same area seen in a and suggests hemorrhage or calcification. (c) On an axial T2-weighted MR image, the mass shows even more heterogeneity, with prominent peripheral areas of marked hypointensity suggestive of deposition of hemosiderin (small arrows). Vasogenic edema (large arrows) is present in the surrounding brain parenchyma. (d) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass.

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 24d.  Intraventricular meningioma. (a) Axial CT image shows a heterogeneous, lobulated mass arising in the atrium of the left lateral ventricle. Subtle region of mild hyperattenuation (arrowhead) is noted along the anteromedial margin of the mass. (b) On an axial T1-weighted MR image, the mass is isointense relative to gray matter. Focal area of hyperintensity (arrowhead) correlates with the same area seen in a and suggests hemorrhage or calcification. (c) On an axial T2-weighted MR image, the mass shows even more heterogeneity, with prominent peripheral areas of marked hypointensity suggestive of deposition of hemosiderin (small arrows). Vasogenic edema (large arrows) is present in the surrounding brain parenchyma. (d) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass.

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 25a.  Intraventricular meningioma in a 16-year-old girl with recurrent syncopal episodes and vertigo. (a) Axial T2-weighted FLAIR image shows a lobulated, hypointense mass (arrow) within the atrium of the right lateral ventricle. (b) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass. (c) Photograph of the resected specimen shows lobulated morphology.

View larger version (108K): [in this window] [in a new window] [Download PPT slide]   Figure 25b.  Intraventricular meningioma in a 16-year-old girl with recurrent syncopal episodes and vertigo. (a) Axial T2-weighted FLAIR image shows a lobulated, hypointense mass (arrow) within the atrium of the right lateral ventricle. (b) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass. (c) Photograph of the resected specimen shows lobulated morphology.

View larger version (114K): [in this window] [in a new window] [Download PPT slide]   Figure 25c.  Intraventricular meningioma in a 16-year-old girl with recurrent syncopal episodes and vertigo. (a) Axial T2-weighted FLAIR image shows a lobulated, hypointense mass (arrow) within the atrium of the right lateral ventricle. (b) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass. (c) Photograph of the resected specimen shows lobulated morphology.

On CT images, intraventricular metastases are either isoattenuated or hyperattenuated (12). On MR images, they are hypointense with short TR pulse sequences and hyperintense with long TR pulse sequences (Fig 26) (12). The lesions typically enhance intensely after the intravenous administration of contrast media (Fig 27) (12).

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 26a.  Renal cell carcinoma with intraventricular metastasis. (a) Abdominal CT image shows a hypoattenuated mass (arrow) within the right kidney, consistent with a renal cell carcinoma. (b) Sagittal T1-weighted MR image shows the heterogeneous mass (arrows) within the lateral ventricle. Hyperintense signal near the top of the mass suggests hemorrhage. (c) Axial T2-weighted MR image shows heterogeneous isointensity within the mass. (d) Lateral view from cerebral angiography shows early blush (arrowheads) in the region of the mass, a finding that reflects the typical hypervascularity associated with renal cell carcinomas.

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 26b.  Renal cell carcinoma with intraventricular metastasis. (a) Abdominal CT image shows a hypoattenuated mass (arrow) within the right kidney, consistent with a renal cell carcinoma. (b) Sagittal T1-weighted MR image shows the heterogeneous mass (arrows) within the lateral ventricle. Hyperintense signal near the top of the mass suggests hemorrhage. (c) Axial T2-weighted MR image shows heterogeneous isointensity within the mass. (d) Lateral view from cerebral angiography shows early blush (arrowheads) in the region of the mass, a finding that reflects the typical hypervascularity associated with renal cell carcinomas.

View larger version (168K): [in this window] [in a new window] [Download PPT slide]   Figure 26c.  Renal cell carcinoma with intraventricular metastasis. (a) Abdominal CT image shows a hypoattenuated mass (arrow) within the right kidney, consistent with a renal cell carcinoma. (b) Sagittal T1-weighted MR image shows the heterogeneous mass (arrows) within the lateral ventricle. Hyperintense signal near the top of the mass suggests hemorrhage. (c) Axial T2-weighted MR image shows heterogeneous isointensity within the mass. (d) Lateral view from cerebral angiography shows early blush (arrowheads) in the region of the mass, a finding that reflects the typical hypervascularity associated with renal cell carcinomas.

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 26d.  Renal cell carcinoma with intraventricular metastasis. (a) Abdominal CT image shows a hypoattenuated mass (arrow) within the right kidney, consistent with a renal cell carcinoma. (b) Sagittal T1-weighted MR image shows the heterogeneous mass (arrows) within the lateral ventricle. Hyperintense signal near the top of the mass suggests hemorrhage. (c) Axial T2-weighted MR image shows heterogeneous isointensity within the mass. (d) Lateral view from cerebral angiography shows early blush (arrowheads) in the region of the mass, a finding that reflects the typical hypervascularity associated with renal cell carcinomas.

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 27a.  Melanoma metastasis. (a) Axial T1-weighted MR image shows a fourth ventricular mass (arrow) that is slightly hypointense compared with the cerebellum. A relative lack of melanin content in this neoplasm produced an atypical imaging appearance, with absence of T1 hyperintensity. (b) On an axial T2-weighted image, the mass is slightly hyperintense compared with the cerebellum. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced sagittal T1-weighted image shows the lobulated appearance of the mass and inferior extension.

View larger version (155K): [in this window] [in a new window] [Download PPT slide]   Figure 27b.  Melanoma metastasis. (a) Axial T1-weighted MR image shows a fourth ventricular mass (arrow) that is slightly hypointense compared with the cerebellum. A relative lack of melanin content in this neoplasm produced an atypical imaging appearance, with absence of T1 hyperintensity. (b) On an axial T2-weighted image, the mass is slightly hyperintense compared with the cerebellum. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced sagittal T1-weighted image shows the lobulated appearance of the mass and inferior extension.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 27c.  Melanoma metastasis. (a) Axial T1-weighted MR image shows a fourth ventricular mass (arrow) that is slightly hypointense compared with the cerebellum. A relative lack of melanin content in this neoplasm produced an atypical imaging appearance, with absence of T1 hyperintensity. (b) On an axial T2-weighted image, the mass is slightly hyperintense compared with the cerebellum. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced sagittal T1-weighted image shows the lobulated appearance of the mass and inferior extension.

View larger version (156K): [in this window] [in a new window] [Download PPT slide]   Figure 27d.  Melanoma metastasis. (a) Axial T1-weighted MR image shows a fourth ventricular mass (arrow) that is slightly hypointense compared with the cerebellum. A relative lack of melanin content in this neoplasm produced an atypical imaging appearance, with absence of T1 hyperintensity. (b) On an axial T2-weighted image, the mass is slightly hyperintense compared with the cerebellum. (c) Contrast-enhanced axial T1-weighted MR image shows intense enhancement of the mass. (d) Contrast-enhanced sagittal T1-weighted image shows the lobulated appearance of the mass and inferior extension.

	Summary

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Neoplasms of the Ventricular... Neoplasms of the Choroid... Summary References

 
By using clinical, demographic, and imaging findings, one can significantly limit the differential diagnosis for many of the most common intraventricular neoplasms. Ependymomas are typically calcified, are more common in children, are more common in the fourth ventricle, and show intense enhancement on contrast-enhanced images. Subependymomas and central neurocytomas have an affinity for the anterior portion of the lateral ventricle and both commonly demonstrate a heterogeneous cystic appearance on cross-sectional images. Subependymomas are more common in older adults, whereas central neurocytomas are more common before 40 years of age. SEGAs always lie near the foramen of Monro and are characterized by frequent calcification, intense enhancement on contrast-enhanced studies, and the presence of other stigmata seen in tuberous sclerosis. When a mass is centered on the choroid plexus, a highly vascular tumor—either choroid plexus papilloma, choroid plexus carcinoma, meningioma, or metastasis—should be suspected. The characteristic heavily lobulated appearance of a choroid plexus tumor favors this diagnosis over other possibilities, although it is not always possible to distinguish between the more common benign form, the choroid plexus papilloma, and the less common malignant counterpart, the choroid plexus carcinoma.

	Acknowledgments

 
The authors gratefully acknowledge the contributions of case material to the Thompson Archives of the Department of Radiologic Pathology at the Armed Forces Institute of Pathology from radiology residents worldwide and the assistance of Sharon Holquin in the preparation of the images.

	Footnotes

 
Abbreviations: CSF = cerebrospinal fluid, SEGA = subependymal giant cell astrocytoma, TR = repetition time, WHO = World Health Organization

The opinions and assertions contained herein are the private views of the authors and are not to be construed as official nor as reflecting the views of the Departments of the Navy, Army, or Defense.

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Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Neoplasms of the Ventricular... Neoplasms of the Choroid... Summary References

 

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