DOI: 10.1148/rg.242035082
RadioGraphics 2004;24:387-404
© RSNA, 2004
Spectrum of Germ Cell Tumors: From Head to Toe1
Teruko Ueno, MD,
Yumiko Oishi Tanaka, MD,
Michio Nagata, MD,
Hajime Tsunoda, MD,
Izumi Anno, MD,
Shigemi Ishikawa, MD,
Koji Kawai, MD and
Yuji Itai, MD
1 From the Department of Radiology, Tsukuba University Hospital, 2-1-1 Amakubo, Tsukuba, Ibaraki 305-8576, Japan (T.U.); and the Departments of Radiology (Y.O.T., I.A., Y.I.), Pathology (M.N.), Obstetrics and Gynecology (H.T.), Thoracic Surgery (S.I.), and Urology (K.K.), University of Tsukuba, Ibaraki, Japan. Presented as an education exhibit at the 2002 RSNA scientific assembly. Received March 27, 2003; revision requested May 30 and received August 18; accepted August 20. All authors have no financial relationships to disclose. Address correspondence to T.U. (e-mail: u-teruko@mua.biglobe.ne.jp).
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Abstract
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Germ cell tumors (GCTs) occur most frequently in the gonads and are relatively rare in other sites, such as the pineal gland, neurohypophysis, mediastinum, and retroperitoneum. GCTs are thought to originate from primordial germ cells, which migrate to the primitive gonadal glands in the urogenital ridge. Extragonadal GCTs might also originate from these cells when the cells are sequestered during their migration. Pathologic subtypes of GCTs vary, and the prevalence of mixed tumors is high. These factors produce a diversity of radiologic findings and make prospective radiologic diagnosis difficult in many cases. However, similar radiologic findings have been observed in pathologically equivalent tumors in varying sites. Seminomas appear as uniformly solid, lobulated masses with fibrovascular septa that enhance intensely. Nonseminomatous GCTs appear as heterogeneous masses with areas of necrosis, hemorrhage, or cystic degeneration. Fat and calcifications are hallmarks of teratomas, most of which are benign. In immature teratomas, scattered fat and calcification within larger solid components are occasionally seen. These imaging characteristics reflect the pathologic features of each tumor, and histologically similar GCTs at varying sites have similar radiologic features. Knowledge of the pathologic appearances of GCTs and their corresponding radiologic appearances will allow radiologists to diagnose these tumors correctly.
© RSNA, 2004
Index Terms: Choriocarcinoma, **.322 • Germ cell neoplasm, **.30 • Seminoma, **.32 • Teratoma, **.30
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LEARNING OBJECTIVES FOR TEST 2
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After reading this article and taking the test, the reader will be able to:
- Discuss the embryologic origin and clinical features of germ cell tumors in various locations.
- Describe the differences in pathologic and radiologic features between seminomas and nonseminomatous germ cell tumors.
- Identify the radiologic characteristics of teratomas.
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Introduction
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Germ cell tumors (GCTs) affect not only the gonads but also extragonadal tissue. The testes and ovaries are the most common sites where GCTs occur; however, the prevalence of GCTs is different at each of these sites. Ninety-five percent of testicular tumors are GCTs; on the other hand, only 30% of ovarian tumors are GCTs. The mediastinum is the second most common site affected by GCTs, with GCTs accounting for 15% of anterior mediastinal tumors in adults and 24% in children. GCTs also occur in the central nervous system, such as the pineal gland, neurohypophysis, and sacrococcygeal region. However, GCTs in these sites are rare.
Although GCTs consist of histologically varying tumors, imaging studies indicate that the histologic features of each tumor variety are similar wherever it occurs. Seminomas, which are known as germinomas in the pineal gland and dysgerminomas in the ovary, usually appear as large, bulky, solid masses with fibrovascular septa. On the other hand, nonseminomatous malignant GCTs, such as embryonal carcinomas, yolk sac tumors, or choriocarcinomas, tend to have a more heterogeneous appearance caused by coexistent hemorrhage and necrosis. Teratomas usually contain sebaceous fat with calcification, and immature teratomas tend to have a large solid component.
Most extragonadal GCTs occur in the median line of the human body. The anterior mediastinum, sacrococcygeal region, pineal gland, and neurohypophysis are common sites. Embryologic and histopathologic considerations suggest two different origins of extragonadal GCTs: metastases from gonadal GCTs and primary GCTs originating from migrated primordial germ cells.
In this article, we present GCTs with varied histologic features and locations, describe the results of imaging-pathologic correlation, and discuss the similarities and differences between the tumor types. We also discuss the embryologic origin, classification, and clinical features of GCTs.
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Embryologic Origin of GCTs
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At the beginning of the 5th gestational week, primordial gonads appear on the medial side of the gonadal ridge. Primordial germ cells are considered to be of yolk sac origin, and these appear in the 5-week embryo. The gonadal ridge extends from the sixth thoracic segment to the second sacral segment (1). In the 6th gestational week, the primordial germ cells migrate into the underlying mesenchyme and become incorporated into the primary sex cords, forming the seminiferous tubules (Fig 1). The primordial germ cells are committed to developing into the spermatogonia or primordial follicles at the primary sex cords, although they might also be the origin of extragonadal GCTs when mismigration occurs. In the 4th to 8th gestational weeks, the yolk sac involutes just near the center of the embryo.
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Figure 1. Development of the primordial gonads. Drawing shows a transverse section of a 5-week embryo. Primordial germ cells migrate from the hindgut to the gonadal ridge. (Adapted and reprinted, with permission, from reference 1.)
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Extragonadal GCTs are made up of tissue that is histologically identical to that in gonadal GCTs. They are thought to be developed from primordial germ cells, which can be misplaced during the long trip to the gonads. Anderson et al (2) reported that primordial germ cells sometimes migrate incorrectly to the allantois, which does not contribute to the germ line. The migration error of the primordial germ cells would inhibit the apoptosis of ectopic primordial germ cells, which are considered the origin of GCTs (3,4). On the other hand, some researchers consider that all extragonadal GCTs are metastases from the testes or ovaries, as no primordial germ cells were found in the extragonadal region and the prevalence of extragonadal GCTs is only 1%–2.5% of all GCTs. However, recent progress in chromosomal (3) and imprinting (4) analysis strongly indicates that mismigrated primordial germ cells are the origin of extragonadal GCTs.
The GCTs exhibit various pathologic features according to the totipotentiality of the tumor cells. Therefore, one-third of the tumors have mixed patterns, and tumors arising from germ cells at different stages of their development should exhibit different features (4–7).
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Classification of GCTs
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The origin of testicular tumors is thought to be atypical cell proliferation, which is termed intratubular germ cell neoplasia (5,6). The degree and direction of the differentiation determine the histologic subtype of the GCTs (Fig 2). Totipotent stem cells in an undifferentiated state give rise to embryonal carcinomas. If the stem cells have progressed toward the extraembryonic pathway, the tumors produced are yolk sac tumors or choriocarcinomas. If the cells have progressed toward the embryonic pathway, they become teratomas.
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Figure 2. Differential pathways of origin for GCTs. Diagram shows the cellular origin of each type of GCT, which is correlated with the differentiation of the primordial germ cells. ITGCN = intratubular germ cell neoplasia.
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Almost the same classification system can be applied to any tumor site. In Table 1, we present the classification of testicular GCTs established by the World Health Organization. GCTs are classified into two categories: seminomas or nonseminomatous GCTs. Nonseminomatous GCTs consist of embryonal carcinomas, yolk sac tumors, and choriocarcinomas.
Seminoma
Pathologic Features.—
A seminoma is not microscopically distinguishable from an ovarian dysgerminoma or intracranial germinoma. At gross analysis, this tumor has a solid, uniform appearance. At microscopic analysis, it is composed of large, round cells with clear cytoplasm, which resemble primordial germ cells. These are supported by varying quantities of lymphoid and granulomatous stroma (5–10). Although hormonal activity is not usually apparent in these tumors, 5%–15% of gonadal and 7%–18% of mediastinal seminomas demonstrate elevated levels of ß–human chorionic gonadotropin produced by accompanying syncytiotrophoblastic giant cells (5–8).
Radiologic Features.—
Radiologic findings for seminomas, dysgerminomas, and germinomas reflect their uniform cellular nature (Table 2, Figs 3–8). The testicle is an organ in which US is instrumental in the search for masses. Testicular seminomas appear as homogeneous hypoechoic masses at US (17) (Fig 8). Doppler US can reveal vessels within the tumor mass or in the fibrous septa. Testicular microlithiasis (Fig 9) is known to be a risk factor for malignant testicular GCTs (18). Recently, however, the prevalence of testicular GCTs in patients with testicular microlithiasis was reported to be lower than initially expected (19).
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Figure 3a. Testicular seminoma in a 51-year-old man with a palpable mass in the right testis. (a) Axial T2-weighted MR image shows a solid mass in the right testis. The mass has a lobulated margin and uniform signal intensity. Bandlike structures of low signal intensity (arrows), which represent fibrovascular septa, are seen within the mass. (b) Axial contrast material-enhanced MR image shows that the septa (arrows) enhance more than the tumor tissue. This finding indicates that the septa include a large amount of vascular structures.
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Figure 3b. Testicular seminoma in a 51-year-old man with a palpable mass in the right testis. (a) Axial T2-weighted MR image shows a solid mass in the right testis. The mass has a lobulated margin and uniform signal intensity. Bandlike structures of low signal intensity (arrows), which represent fibrovascular septa, are seen within the mass. (b) Axial contrast material-enhanced MR image shows that the septa (arrows) enhance more than the tumor tissue. This finding indicates that the septa include a large amount of vascular structures.
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Figure 4a. Dysgerminoma of the ovary in a 31-year-old woman with fever and abdominal pain. (a) Sagittal T2-weighted MR image shows a large, lobulated solid mass in the pelvis and lower abdomen. Fibrovascular septa are seen as low-signal-intensity bands (arrows). (b) Sagittal contrast-enhanced T1-weighted MR image shows clear enhancement of the septa (arrows). (c) Photomicrograph (original magnification, x400; hematoxylin-eosin [H-E] stain) shows that the tumor is composed of large, round cells containing clear cytoplasm and irregularly flattened nuclei. (d) Photomicrograph (original magnification, x40; H-E stain) shows that the clusters of tumor cells are divided by fibrous septa, which include lymphocytes.
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Figure 4b. Dysgerminoma of the ovary in a 31-year-old woman with fever and abdominal pain. (a) Sagittal T2-weighted MR image shows a large, lobulated solid mass in the pelvis and lower abdomen. Fibrovascular septa are seen as low-signal-intensity bands (arrows). (b) Sagittal contrast-enhanced T1-weighted MR image shows clear enhancement of the septa (arrows). (c) Photomicrograph (original magnification, x400; hematoxylin-eosin [H-E] stain) shows that the tumor is composed of large, round cells containing clear cytoplasm and irregularly flattened nuclei. (d) Photomicrograph (original magnification, x40; H-E stain) shows that the clusters of tumor cells are divided by fibrous septa, which include lymphocytes.
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Figure 4c. Dysgerminoma of the ovary in a 31-year-old woman with fever and abdominal pain. (a) Sagittal T2-weighted MR image shows a large, lobulated solid mass in the pelvis and lower abdomen. Fibrovascular septa are seen as low-signal-intensity bands (arrows). (b) Sagittal contrast-enhanced T1-weighted MR image shows clear enhancement of the septa (arrows). (c) Photomicrograph (original magnification, x400; hematoxylin-eosin [H-E] stain) shows that the tumor is composed of large, round cells containing clear cytoplasm and irregularly flattened nuclei. (d) Photomicrograph (original magnification, x40; H-E stain) shows that the clusters of tumor cells are divided by fibrous septa, which include lymphocytes.
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Figure 4d. Dysgerminoma of the ovary in a 31-year-old woman with fever and abdominal pain. (a) Sagittal T2-weighted MR image shows a large, lobulated solid mass in the pelvis and lower abdomen. Fibrovascular septa are seen as low-signal-intensity bands (arrows). (b) Sagittal contrast-enhanced T1-weighted MR image shows clear enhancement of the septa (arrows). (c) Photomicrograph (original magnification, x400; hematoxylin-eosin [H-E] stain) shows that the tumor is composed of large, round cells containing clear cytoplasm and irregularly flattened nuclei. (d) Photomicrograph (original magnification, x40; H-E stain) shows that the clusters of tumor cells are divided by fibrous septa, which include lymphocytes.
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Figure 5a. Germinoma of the pineal gland in an 11-month-old boy with sporadic vomiting. Because no abdominal cause was found, the brain was examined. (a) Nonenhanced computed tomographic (CT) scan shows a partly calcified mass in the pineal region (arrow). (b, c) Sagittal T2-weighted (b) and contrast-enhanced T1-weighted (c) MR images show that the mass (black arrows in b) is solid with small cysts and marked enhancement. The tumor extends upward, compressing and displacing the internal cerebral vein (white arrows in b). (d) Photomicrograph (original magnification, x400; H-E stain) shows that the tumor is composed of large, rounded cells with clear cytoplasm.
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Figure 5b. Germinoma of the pineal gland in an 11-month-old boy with sporadic vomiting. Because no abdominal cause was found, the brain was examined. (a) Nonenhanced computed tomographic (CT) scan shows a partly calcified mass in the pineal region (arrow). (b, c) Sagittal T2-weighted (b) and contrast-enhanced T1-weighted (c) MR images show that the mass (black arrows in b) is solid with small cysts and marked enhancement. The tumor extends upward, compressing and displacing the internal cerebral vein (white arrows in b). (d) Photomicrograph (original magnification, x400; H-E stain) shows that the tumor is composed of large, rounded cells with clear cytoplasm.
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Figure 5c. Germinoma of the pineal gland in an 11-month-old boy with sporadic vomiting. Because no abdominal cause was found, the brain was examined. (a) Nonenhanced computed tomographic (CT) scan shows a partly calcified mass in the pineal region (arrow). (b, c) Sagittal T2-weighted (b) and contrast-enhanced T1-weighted (c) MR images show that the mass (black arrows in b) is solid with small cysts and marked enhancement. The tumor extends upward, compressing and displacing the internal cerebral vein (white arrows in b). (d) Photomicrograph (original magnification, x400; H-E stain) shows that the tumor is composed of large, rounded cells with clear cytoplasm.
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Figure 5d. Germinoma of the pineal gland in an 11-month-old boy with sporadic vomiting. Because no abdominal cause was found, the brain was examined. (a) Nonenhanced computed tomographic (CT) scan shows a partly calcified mass in the pineal region (arrow). (b, c) Sagittal T2-weighted (b) and contrast-enhanced T1-weighted (c) MR images show that the mass (black arrows in b) is solid with small cysts and marked enhancement. The tumor extends upward, compressing and displacing the internal cerebral vein (white arrows in b). (d) Photomicrograph (original magnification, x400; H-E stain) shows that the tumor is composed of large, rounded cells with clear cytoplasm.
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Figure 6a. Suprasellar germinoma in a 38-year-old woman with amenorrhea. (a, b) Sagittal T2-weighted (a) and contrast-enhanced fat-saturated T1-weighted (b) MR images show a solid mass with a cystic area (arrow in a) and marked enhancement. The pituitary gland is compressed and flattened along the sellar floor (arrows in b). The tumor extends upward toward the infundibular recess. (c) Photomicrograph (original magnification, x400; H-E stain) shows uniformly proliferating tumor cells. In contrast to ovarian dysgerminoma, few fibrous septa are seen.
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Figure 6b. Suprasellar germinoma in a 38-year-old woman with amenorrhea. (a, b) Sagittal T2-weighted (a) and contrast-enhanced fat-saturated T1-weighted (b) MR images show a solid mass with a cystic area (arrow in a) and marked enhancement. The pituitary gland is compressed and flattened along the sellar floor (arrows in b). The tumor extends upward toward the infundibular recess. (c) Photomicrograph (original magnification, x400; H-E stain) shows uniformly proliferating tumor cells. In contrast to ovarian dysgerminoma, few fibrous septa are seen.
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Figure 6c. Suprasellar germinoma in a 38-year-old woman with amenorrhea. (a, b) Sagittal T2-weighted (a) and contrast-enhanced fat-saturated T1-weighted (b) MR images show a solid mass with a cystic area (arrow in a) and marked enhancement. The pituitary gland is compressed and flattened along the sellar floor (arrows in b). The tumor extends upward toward the infundibular recess. (c) Photomicrograph (original magnification, x400; H-E stain) shows uniformly proliferating tumor cells. In contrast to ovarian dysgerminoma, few fibrous septa are seen.
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Figure 7a. Seminoma of the mediastinum in a 37-year-old man with edema and swelling of the face and neck but no other symptoms. Chest radiography indicated a tumor of the upper mediastinum. (a) Axial T2-weighted MR image shows a large lobulated mass with several fibrovascular septa (arrows). (b) Axial contrast-enhanced T1-weighted MR image shows marked enhancement of the septa (arrows). (c) Photomicrograph (original magnification, x400; H-E stain) shows that the tumor is composed of large, rounded, clear cells.
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Figure 7b. Seminoma of the mediastinum in a 37-year-old man with edema and swelling of the face and neck but no other symptoms. Chest radiography indicated a tumor of the upper mediastinum. (a) Axial T2-weighted MR image shows a large lobulated mass with several fibrovascular septa (arrows). (b) Axial contrast-enhanced T1-weighted MR image shows marked enhancement of the septa (arrows). (c) Photomicrograph (original magnification, x400; H-E stain) shows that the tumor is composed of large, rounded, clear cells.
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Figure 7c. Seminoma of the mediastinum in a 37-year-old man with edema and swelling of the face and neck but no other symptoms. Chest radiography indicated a tumor of the upper mediastinum. (a) Axial T2-weighted MR image shows a large lobulated mass with several fibrovascular septa (arrows). (b) Axial contrast-enhanced T1-weighted MR image shows marked enhancement of the septa (arrows). (c) Photomicrograph (original magnification, x400; H-E stain) shows that the tumor is composed of large, rounded, clear cells.
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Figure 8a. Pure testicular seminoma in a 30-year-old man. (a) Ultrasonographic (US) scan shows a multinodular tumor in the right testis. The tumor is divided by fibrous septa, which appear as hypoechoic bands (arrow). No cystic component is seen. (b) Color Doppler image shows that the septa are richly vascularized (arrowhead).
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Figure 8b. Pure testicular seminoma in a 30-year-old man. (a) Ultrasonographic (US) scan shows a multinodular tumor in the right testis. The tumor is divided by fibrous septa, which appear as hypoechoic bands (arrow). No cystic component is seen. (b) Color Doppler image shows that the septa are richly vascularized (arrowhead).
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These tumors appear as large, lobulated, well-marginated, and uniformly homogeneous masses on CT and MR images. A characteristic structure of these tumors is a network of fibrovascular septa, which is discernible as a hypointense bandlike structure on T2-weighted images. The septa are strikingly enhanced on both CT and MR images (Figs 3, 4, 7). These fibrous septa usually contain lymphocytes and blood vessels, which are visualized microscopically (7–9). Calcification is rare and appears as a speckled, ringlike, or stippled pattern when present (9,20). It is very rare that these tumors have a cystic component, unlike nonseminomatous GCTs.
In intracranial germinomas, fibrous septa are not as prominent as in dysgerminomas of the ovary (Figs 5, 6). Less than 10% of intracranial germinomas occur in the basal ganglia (21–23). These tumors are not very large because symptoms appear early in tumors at this site. Fibrous septa are also apparent in mediastinal seminomas (Fig 7) (9). Although the exact cause of the prominent cystic changes is unknown, a mediastinal seminoma appearing as a multiloculated cyst has also been reported (24).
Nonseminomatous GCTs
Pathologic Features.—
An embryonal carcinoma is composed of cells with an embryonic and anaplastic epithelial appearance. Tumor cells proliferate in an acinar, tubular, papillary, or solid pattern. Punctate foci of hemorrhage or necrosis are often seen. In contrast to seminoma, the border of each cell is usually indistinct. This tumor is well known as an 
-fetoprotein–producing tumor (8). A yolk sac tumor demonstrates a reticular pattern characterized by a loose meshwork of communicating spaces lined by primitive tumor cells. Each cell has hyperchromatic, bizarre nuclei. The Schillar-Duval body, which consists of single papillae with fibrovascular cores containing single vessels, is another characteristic of this tumor (5,7). This tumor is also known to be an -fetoprotein–producing tumor. Choriocarcinomas are composed solely of cytotrophoblastic and syncytiotrophoblastic cells that produce ß–human chorionic gonadotropin. Intratumoral hemorrhage and necrosis are quite common. Most gonadal choriocarcinomas develop as mixed GCTs.
Radiologic Features.—
Nonseminomatous GCTs are reported to be heterogeneous masses with areas of hemorrhage and necrosis (Figs 10, 11). Hemorrhage and necrosis are much more frequent in nonseminomatous GCTs than in seminomas, especially in choriocarcinomas (Fig 12) and yolk sac tumors (Fig 13) (5–8). Therefore, hypoattenuating unenhanced areas at CT are very common. These are also demonstrated as areas without contrast enhancement at MR imaging. Hemorrhage may be seen as hyperintense areas on T1-weighted images. Flow voids, which correspond to hypervascularity, are occasionally seen within yolk sac tumors of the ovary (25). Patterns of contrast enhancement have also been reported as heterogeneous. Nonseminomatous GCTs often invade the adjacent organs (Figs 10, 13), thereby demonstrating ill-defined, irregular margins. Pleural effusion, ascites, and lymphadenopathy have also been reported (9,15).
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Figure 10a. Mixed GCT of the anterior mediastinum in a 22-year-old man with dyspnea. Chest radiography indicated that the left thorax was filled with tumor tissue. (a) Coronal T2-weighted MR image shows a large, heterogeneous mediastinal mass that invades the left pleural cavity. The heart, great vessels, and left lung are markedly compressed (arrows). (b) Contrast-enhanced CT scan shows that most of the tumor appears solid, although a relatively large cystic component is seen (arrow). Surgical exploration was followed by chemotherapy. (c) Photomicrograph (original magnification, x400; H-E stain) shows a small amount of immature neural tissue. In addition, serum levels of human chorionic gonadotropin and -fetoprotein were very high at admission. The tumor was diagnosed as a mixed GCT that included an immature teratoma.
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Figure 10b. Mixed GCT of the anterior mediastinum in a 22-year-old man with dyspnea. Chest radiography indicated that the left thorax was filled with tumor tissue. (a) Coronal T2-weighted MR image shows a large, heterogeneous mediastinal mass that invades the left pleural cavity. The heart, great vessels, and left lung are markedly compressed (arrows). (b) Contrast-enhanced CT scan shows that most of the tumor appears solid, although a relatively large cystic component is seen (arrow). Surgical exploration was followed by chemotherapy. (c) Photomicrograph (original magnification, x400; H-E stain) shows a small amount of immature neural tissue. In addition, serum levels of human chorionic gonadotropin and -fetoprotein were very high at admission. The tumor was diagnosed as a mixed GCT that included an immature teratoma.
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Figure 10c. Mixed GCT of the anterior mediastinum in a 22-year-old man with dyspnea. Chest radiography indicated that the left thorax was filled with tumor tissue. (a) Coronal T2-weighted MR image shows a large, heterogeneous mediastinal mass that invades the left pleural cavity. The heart, great vessels, and left lung are markedly compressed (arrows). (b) Contrast-enhanced CT scan shows that most of the tumor appears solid, although a relatively large cystic component is seen (arrow). Surgical exploration was followed by chemotherapy. (c) Photomicrograph (original magnification, x400; H-E stain) shows a small amount of immature neural tissue. In addition, serum levels of human chorionic gonadotropin and -fetoprotein were very high at admission. The tumor was diagnosed as a mixed GCT that included an immature teratoma.
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Figure 11a. Embryonal carcinoma of the pineal gland in a 32-year-old man with double vision. The brain was examined with MR imaging. (a) Axial T2-weighted MR image shows a tumor with heterogeneous signal intensity in the pineal gland (arrows). (b) Axial contrast-enhanced T1-weighted MR image shows some enhancing foci within the tumor (arrows). (c) Photomicrograph (original magnification, x200; H-E stain) shows embryonal cells with an epithelial appearance growing in a tubular pattern. Glandular, papillary, and solid reticular patterns are also present.
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Figure 11b. Embryonal carcinoma of the pineal gland in a 32-year-old man with double vision. The brain was examined with MR imaging. (a) Axial T2-weighted MR image shows a tumor with heterogeneous signal intensity in the pineal gland (arrows). (b) Axial contrast-enhanced T1-weighted MR image shows some enhancing foci within the tumor (arrows). (c) Photomicrograph (original magnification, x200; H-E stain) shows embryonal cells with an epithelial appearance growing in a tubular pattern. Glandular, papillary, and solid reticular patterns are also present.
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Figure 11c. Embryonal carcinoma of the pineal gland in a 32-year-old man with double vision. The brain was examined with MR imaging. (a) Axial T2-weighted MR image shows a tumor with heterogeneous signal intensity in the pineal gland (arrows). (b) Axial contrast-enhanced T1-weighted MR image shows some enhancing foci within the tumor (arrows). (c) Photomicrograph (original magnification, x200; H-E stain) shows embryonal cells with an epithelial appearance growing in a tubular pattern. Glandular, papillary, and solid reticular patterns are also present.
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Figure 12a. Mixed GCT (combined seminoma and choriocarcinoma) of the testis in a 31-year-old man with an enlarged testis containing a palpable mass. (a) Coronal T2-weighted MR image shows a smoothly marginated, rounded tumor. Although the upper part of the tumor appears homogeneously solid, the lower part is cystic. (b) Coronal contrast-enhanced T1-weighted MR image shows some fibrovascular septa (arrow), which are indicative of a seminoma. At pathologic analysis of the resected specimen, the upper part of the tumor was diagnosed as a seminoma. (c) Photomicrograph (original magnification, x400; H-E stain) of the lower part of the tumor shows both syncytiotrophoblasts (black arrow) and cytotrophoblasts (white arrow) with hemorrhage.
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Figure 12b. Mixed GCT (combined seminoma and choriocarcinoma) of the testis in a 31-year-old man with an enlarged testis containing a palpable mass. (a) Coronal T2-weighted MR image shows a smoothly marginated, rounded tumor. Although the upper part of the tumor appears homogeneously solid, the lower part is cystic. (b) Coronal contrast-enhanced T1-weighted MR image shows some fibrovascular septa (arrow), which are indicative of a seminoma. At pathologic analysis of the resected specimen, the upper part of the tumor was diagnosed as a seminoma. (c) Photomicrograph (original magnification, x400; H-E stain) of the lower part of the tumor shows both syncytiotrophoblasts (black arrow) and cytotrophoblasts (white arrow) with hemorrhage.
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Figure 12c. Mixed GCT (combined seminoma and choriocarcinoma) of the testis in a 31-year-old man with an enlarged testis containing a palpable mass. (a) Coronal T2-weighted MR image shows a smoothly marginated, rounded tumor. Although the upper part of the tumor appears homogeneously solid, the lower part is cystic. (b) Coronal contrast-enhanced T1-weighted MR image shows some fibrovascular septa (arrow), which are indicative of a seminoma. At pathologic analysis of the resected specimen, the upper part of the tumor was diagnosed as a seminoma. (c) Photomicrograph (original magnification, x400; H-E stain) of the lower part of the tumor shows both syncytiotrophoblasts (black arrow) and cytotrophoblasts (white arrow) with hemorrhage.
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Figure 13a. Yolk sac tumor of the sacrococcygeal region in a 7-month-old girl. A cystic teratoma of the sacrococcygeal region was found at birth. After surgical resection, the tumor grew again. (a, b) Sagittal T1-weighted (a) and T2-weighted (b) MR images show a heterogeneous sacrococcygeal mass with high signal intensity (white arrows). The dorsal part of the tumor appears cystic, and fatty tissue is not evident. The tumor margin is ill defined with infiltration of adjacent tissue (black arrow). (c) Photomicrograph (original magnification, x200; H-E stain) shows a reticular pattern, which is characterized by a loose meshwork of communicating spaces lined by primitive tumor cells. The neoplastic cells have hyperchromatic, irregular nuclei with unusual shapes. A glomeruloid body is seen (arrows), which is a characteristic feature of yolk sac tumors. (d) Photomicrograph (original magnification, x400; -fetoprotein immunohistochemical stain) shows that the tumor contains yolk sac epithelium.
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Figure 13b. Yolk sac tumor of the sacrococcygeal region in a 7-month-old girl. A cystic teratoma of the sacrococcygeal region was found at birth. After surgical resection, the tumor grew again. (a, b) Sagittal T1-weighted (a) and T2-weighted (b) MR images show a heterogeneous sacrococcygeal mass with high signal intensity (white arrows). The dorsal part of the tumor appears cystic, and fatty tissue is not evident. The tumor margin is ill defined with infiltration of adjacent tissue (black arrow). (c) Photomicrograph (original magnification, x200; H-E stain) shows a reticular pattern, which is characterized by a loose meshwork of communicating spaces lined by primitive tumor cells. The neoplastic cells have hyperchromatic, irregular nuclei with unusual shapes. A glomeruloid body is seen (arrows), which is a characteristic feature of yolk sac tumors. (d) Photomicrograph (original magnification, x400; -fetoprotein immunohistochemical stain) shows that the tumor contains yolk sac epithelium.
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Figure 13c. Yolk sac tumor of the sacrococcygeal region in a 7-month-old girl. A cystic teratoma of the sacrococcygeal region was found at birth. After surgical resection, the tumor grew again. (a, b) Sagittal T1-weighted (a) and T2-weighted (b) MR images show a heterogeneous sacrococcygeal mass with high signal intensity (white arrows). The dorsal part of the tumor appears cystic, and fatty tissue is not evident. The tumor margin is ill defined with infiltration of adjacent tissue (black arrow). (c) Photomicrograph (original magnification, x200; H-E stain) shows a reticular pattern, which is characterized by a loose meshwork of communicating spaces lined by primitive tumor cells. The neoplastic cells have hyperchromatic, irregular nuclei with unusual shapes. A glomeruloid body is seen (arrows), which is a characteristic feature of yolk sac tumors. (d) Photomicrograph (original magnification, x400; -fetoprotein immunohistochemical stain) shows that the tumor contains yolk sac epithelium.
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Figure 13d. Yolk sac tumor of the sacrococcygeal region in a 7-month-old girl. A cystic teratoma of the sacrococcygeal region was found at birth. After surgical resection, the tumor grew again. (a, b) Sagittal T1-weighted (a) and T2-weighted (b) MR images show a heterogeneous sacrococcygeal mass with high signal intensity (white arrows). The dorsal part of the tumor appears cystic, and fatty tissue is not evident. The tumor margin is ill defined with infiltration of adjacent tissue (black arrow). (c) Photomicrograph (original magnification, x200; H-E stain) shows a reticular pattern, which is characterized by a loose meshwork of communicating spaces lined by primitive tumor cells. The neoplastic cells have hyperchromatic, irregular nuclei with unusual shapes. A glomeruloid body is seen (arrows), which is a characteristic feature of yolk sac tumors. (d) Photomicrograph (original magnification, x400; -fetoprotein immunohistochemical stain) shows that the tumor contains yolk sac epithelium.
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In the sacrococcygeal region, more than 60% of GCTs are mature teratomas. Radiologists must suspect malignant GCTs when they find tumors without fat, especially in children older than infants (Fig 13) (26).
Teratomas
Pathologic Features.—
Teratomas contain elements derived from the three germ cell layers: endoderm, mesoderm, and ectoderm. Most teratomas are predominantly cystic, with an epithelial lining resembling the epidermis with its appendages. These tumors usually contain sebaceous fat, which is a characteristic of this tumor and is identifiable radiologically (8).
Radiologic Features.—
Most mature teratomas are predominantly cystic, lined by epithelium resembling epidermis with its appendages. In addition, 93% of tumors contain sebaceous fat. This tumor is exclusively benign; however, 1%–2% of ovarian teratomas (8) and 2%–3% of testicular teratomas (27) undergo malignant transformation, mainly into squamous cell carcinomas (75%) (8). The tumor is a rounded, sharply marginated mass in gross appearance. Solid parts composed of histologically varying elements, which are called a Rokitansky protuberance, are observed in 81% of tumors. Toothlike calcifications are often seen within the tumor. Calcification is another hallmark of this tumor; however, toothlike or rim calcifications are apparent in only 56% of tumors.
At MR imaging, sebaceous fat within the tumor produces characteristically high signal intensity on T1-weighted images. Hyperintense foci produced by fat within ovarian tumors almost always allow specific diagnosis of teratomas; chemical shift between the fatty and watery contents is a diagnostic finding at MR imaging. In addition to the detection of fat, gravity-dependent layering, palm tree–like protrusions (Rokitansky protuberance [Figs 14, 15]), and fat-fluid levels are other imaging characteristics of mature cystic teratomas (16,28). A cauliflower-like projection or thickening of the wall with an irregular margin is reported to be a sign of malignant transformation of mature teratomas, especially when they extend transmurally or invade neighboring pelvic organs (29–31). Malignant transformation of teratomas has also been reported in the mediastinum, stomach, brain, and sacrococcygeal region (29).
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Figure 14a. Mature cystic teratoma of the ovary in a 46-year-old woman. A tumor of the lower abdomen was discovered during a medical checkup. The tumor had caused no complications. (a, b) Axial T1-weighted (a) and T2-weighted (b) MR images show a rounded cystic mass that includes fat and a solid component (arrow) with a palm tree-like appearance. (c) Axial fat-saturated T1-weighted MR image shows decreased signal intensity of the cystic component (arrows). (d) CT scan shows coarse calcifications (arrow).
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Figure 14b. Mature cystic teratoma of the ovary in a 46-year-old woman. A tumor of the lower abdomen was discovered during a medical checkup. The tumor had caused no complications. (a, b) Axial T1-weighted (a) and T2-weighted (b) MR images show a rounded cystic mass that includes fat and a solid component (arrow) with a palm tree-like appearance. (c) Axial fat-saturated T1-weighted MR image shows decreased signal intensity of the cystic component (arrows). (d) CT scan shows coarse calcifications (arrow).
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Figure 14c. Mature cystic teratoma of the ovary in a 46-year-old woman. A tumor of the lower abdomen was discovered during a medical checkup. The tumor had caused no complications. (a, b) Axial T1-weighted (a) and T2-weighted (b) MR images show a rounded cystic mass that includes fat and a solid component (arrow) with a palm tree-like appearance. (c) Axial fat-saturated T1-weighted MR image shows decreased signal intensity of the cystic component (arrows). (d) CT scan shows coarse calcifications (arrow).
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Figure 14d. Mature cystic teratoma of the ovary in a 46-year-old woman. A tumor of the lower abdomen was discovered during a medical checkup. The tumor had caused no complications. (a, b) Axial T1-weighted (a) and T2-weighted (b) MR images show a rounded cystic mass that includes fat and a solid component (arrow) with a palm tree-like appearance. (c) Axial fat-saturated T1-weighted MR image shows decreased signal intensity of the cystic component (arrows). (d) CT scan shows coarse calcifications (arrow).
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Figure 15a. Mature teratoma of the anterior mediastinum in a 29-year-old woman with no symptoms. A mediastinal mass was found at chest radiography. (a, b) Contrast-enhanced CT scans (a obtained cephalad to b) show a huge anterior mediastinal mass protruding into an interlobular fissure of the left lung. No calcification is seen in this case. (c) Photomicrograph (original magnification, x200; H-E stain) shows that the tumor contains a liquid-like pancreatic juice produced by mature pancreatic glands within the tumor.
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Figure 15b. Mature teratoma of the anterior mediastinum in a 29-year-old woman with no symptoms. A mediastinal mass was found at chest radiography. (a, b) Contrast-enhanced CT scans (a obtained cephalad to b) show a huge anterior mediastinal mass protruding into an interlobular fissure of the left lung. No calcification is seen in this case. (c) Photomicrograph (original magnification, x200; H-E stain) shows that the tumor contains a liquid-like pancreatic juice produced by mature pancreatic glands within the tumor.
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Figure 15c. Mature teratoma of the anterior mediastinum in a 29-year-old woman with no symptoms. A mediastinal mass was found at chest radiography. (a, b) Contrast-enhanced CT scans (a obtained cephalad to b) show a huge anterior mediastinal mass protruding into an interlobular fissure of the left lung. No calcification is seen in this case. (c) Photomicrograph (original magnification, x200; H-E stain) shows that the tumor contains a liquid-like pancreatic juice produced by mature pancreatic glands within the tumor.
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Immature teratomas contain variable quantities of immature neural tissue. At gross examination, these tumors are large, encapsulated masses with a rich solid component, which are composed of immature neuroectodermal tissue. Dermoid cysts can be identified in approximately 25% of cases (8). Immature elements are usually recognized as solid parts at CT and MR imaging (14,16,28,32). The existence of a solid component can be a sign of an immature teratoma(Figs 16, 17), although mature teratomas sometimes have large solid parts (Rokitansky protuberances). In addition, immature teratomas without such prominent solid parts are occasionally seen (Fig 18). Serum levels of -fetoprotein increase in only 50% of cases (8).
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Figure 16a. Immature teratoma of the ovary in a 2-year-old girl with abdominal swelling and abdominal pain during defecation. (a, b) Axial T2-weighted (a) and T1-weighted (b) MR images show a huge solid mass with scattered fat and calcification in the supravesical inframesocolic space. (c) Axial fat-saturated T1-weighted MR image shows intense enhancement of the solid component. (d) Photomicrograph (original magnification, x400; H-E stain) of the resected specimen shows that the solid component is composed of immature neuroectodermal tissue, which forms primitive intraepithelial rosettes and tubules. Scattered fat, which has been reported to be a sign of immature elements and consists of well-differentiated fatty tissue, was visible at microscopy.
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Figure 16b. Immature teratoma of the ovary in a 2-year-old girl with abdominal swelling and abdominal pain during defecation. (a, b) Axial T2-weighted (a) and T1-weighted (b) MR images show a huge solid mass with scattered fat and calcification in the supravesical inframesocolic space. (c) Axial fat-saturated T1-weighted MR image shows intense enhancement of the solid component. (d) Photomicrograph (original magnification, x400; H-E stain) of the resected specimen shows that the solid component is composed of immature neuroectodermal tissue, which forms primitive intraepithelial rosettes and tubules. Scattered fat, which has been reported to be a sign of immature elements and consists of well-differentiated fatty tissue, was visible at microscopy.
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Figure 16c. Immature teratoma of the ovary in a 2-year-old girl with abdominal swelling and abdominal pain during defecation. (a, b) Axial T2-weighted (a) and T1-weighted (b) MR images show a huge solid mass with scattered fat and calcification in the supravesical inframesocolic space. (c) Axial fat-saturated T1-weighted MR image shows intense enhancement of the solid component. (d) Photomicrograph (original magnification, x400; H-E stain) of the resected specimen shows that the solid component is composed of immature neuroectodermal tissue, which forms primitive intraepithelial rosettes and tubules. Scattered fat, which has been reported to be a sign of immature elements and consists of well-differentiated fatty tissue, was visible at microscopy.
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Figure 16d. Immature teratoma of the ovary in a 2-year-old girl with abdominal swelling and abdominal pain during defecation. (a, b) Axial T2-weighted (a) and T1-weighted (b) MR images show a huge solid mass with scattered fat and calcification in the supravesical inframesocolic space. (c) Axial fat-saturated T1-weighted MR image shows intense enhancement of the solid component. (d) Photomicrograph (original magnification, x400; H-E stain) of the resected specimen shows that the solid component is composed of immature neuroectodermal tissue, which forms primitive intraepithelial rosettes and tubules. Scattered fat, which has been reported to be a sign of immature elements and consists of well-differentiated fatty tissue, was visible at microscopy.
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Figure 17a. Immature teratoma of the mediastinum in an 11-year-old boy with a persistent cough and fever. Chest radiograph (a) and contrast-enhanced CT scan (b) show a huge mass with a clear margin that extends into both sides of the mediastinum. (Compare the mature teratoma with unilateral protrusion in | |
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Abstract
LEARNING OBJECTIVES FOR TEST...
