DOI: 10.1148/rg.236015527
(Radiographics. 2003;23:1491-1508.)
© RSNA, 2003
Chest Wall Tumors: Radiologic Findings and Pathologic Correlation
Part 2. Malignant Tumors1
Ukihide Tateishi, MD, PhD,
Gregory W. Gladish, MD,
Masahiko Kusumoto, MD, PhD,
Tadashi Hasegawa, MD, PhD,
Ryohei Yokoyama, MD,
Ryosuke Tsuchiya, MD, PhD and
Noriyuki Moriyama, MD, PhD
1 From the Divisions of Diagnostic Radiology (U.T., M.K., N.M.), Pathology (T.H.), Orthopedics (R.Y.), and Thoracic Surgery (R.T.), National Cancer Center Hospital and Institute, 5–1-1, Tsukiji, Chuo-Ku, 104-0045 Tokyo, Japan; Division of Diagnostic Imaging, M. D. Anderson Cancer Center, Houston, Tex (G.W.G.); and Division of Orthopedics, National Kyushu Cancer Center, Fukuoka, Japan (R.Y.). Recipient of a Cum Laude award for an education exhibit at the 2001 RSNA scientific assembly. Received December 20, 2001; revision requested February 22, 2002; revision received April 22, 2003 and accepted April 25. Supported in part by grant for Scientific Research Expenses for Health and Welfare Programs, the Foundation for the Promotion of Cancer Research, and 2nd-term Comprehensive 10-year Strategy for Cancer Control. Address correspondence to U.T. (e-mail: utateish@ncc.go.jp).
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Abstract
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Malignant chest wall tumors are classified into eight main diagnostic categories: muscular, vascular, fibrous and fibrohistiocytic, peripheral nerve, osseous and cartilaginous, adipose, hematologic, and cutaneous. However, there are malignant tumors that arise in the chest wall and that do not fit well in any of these categories (eg, Ewing sarcoma and synovial sarcoma). Malignant chest wall tumors typically manifest as painful, rapidly growing, large palpable masses. Chest radiography, the technique most often used for initial evaluation, can be helpful for detecting cortical destruction. However, computed tomography is more sensitive than chest radiography for detecting calcified tumor matrix and cortical destruction. Magnetic resonance imaging often allows more accurate delineation and localization of the tumor and is helpful for determining the presence and extent of tumor invasion and for tissue characterization. Although the imaging features of many malignant chest wall tumors are nonspecific, knowledge of the typical radiologic manifestations of these tumors often enables their differentiation from benign chest wall tumors and occasionally allows a specific diagnosis to be suggested. The article reviews the clinical and imaging features of the most common malignant chest wall tumors and presents images collected at a single cancer referral center.
© RSNA, 2003
Index Terms: Thorax, CT, 470.1211 • Thorax, MR, 470.12141, 470.12143 • Thorax, neoplasms, 470.32, 470.34, 470.37 • Thorax, radiography, 470.11
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LEARNING OBJECTIVES
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After reading this article and taking the test, the reader will be able to:
- Recognize the imaging signs that may be helpful in achieving differential diagnosis of malignant chest wall tumors.
- Describe the individual pathologic entities and processes involved in the most frequently occurring malignant chest wall tumors.
- Identify the characteristic imaging findings in major malignant chest wall tumors.
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Introduction
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Primary malignant chest wall tumors typically manifest as large, palpable, rapidly growing masses (1). Chest wall pain is a common symptom, and most patients with malignant chest wall tumors are symptomatic, unlike patients with benign chest wall tumors (1–3). Malignant chest wall tumors are classified into eight main diagnostic categories: muscular, vascular, fibrous and fibrohistiocytic, peripheral nerve, osseous and cartilaginous, adipose, hematologic, and cutaneous. Although the imaging features of many malignant chest wall tumors are nonspecific, knowledge of the typical radiologic manifestations of these tumors often enables their differentiation from benign chest wall tumors and occasionally allows a specific diagnosis to be suggested. This article reviews the clinical and imaging features of the most frequently occurring malignant chest wall tumors, emphasizing the features that can be most useful in suggesting a specific diagnosis and differentiating benign from malignant tumors (Tables 1, 2).
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Imaging Techniques and Findings: An Overview
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Chest radiography often is performed at initial evaluation of a clinically suspected malignant chest wall tumor. Although this technique is useful for detecting cortical destruction—a finding indicative of extracompartmental extension—it does not allow comprehensive assessment of the tumor. Computed tomography (CT) is more sensitive than chest radiography for detecting calcified tumor matrix and cortical destruction. Furthermore, magnetic resonance (MR) imaging, which has a multiplanar capability and offers superior spatial resolution, can provide additional information regarding the extent of the tumor, as well as tissue characterization.
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Muscular Tumors
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Leiomyosarcoma
Cutaneous and subcutaneous leiomyosarcomas account for less than 5% of superficial soft-tissue sarcomas. These tumors are frequently painful and typically occur in adulthood, most commonly in men aged 50–70 years. An association of Epstein-Barr virus with leiomyosarcoma has been noted in case reports of children and young adults (age <25 years) with AIDS and of patients who have undergone immunosuppressive therapy after organ transplantation (4,5). However, whether Epstein-Barr viral infection plays a role in the pathogenesis of leiomyosarcoma in immunodeficient patients is still unknown. Most primary leiomyosarcomas are solitary lesions; lesion multiplicity suggests metastasis from another site (6). CT scans in leiomyosarcoma show a large mass that frequently includes areas of necrotic or cystic change. In addition, displacement or distortion of vessels often is seen. Typical MR imaging features of the mass include a spindle shape and long T1 and T2 relaxation times with resultant relatively low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. A finding of overall low signal intensity or of components with low signal intensity on MR images, however, is not specific to leiomyosarcoma. After intravenous administration of contrast material, tumors typically exhibit an enhanced rim or periphery and a central area of low signal intensity or low attenuation (Fig 1).
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Figure 1. Leiomyosarcoma in a 49-year-old woman. Sagittal T1-weighted (repetition time msec/echo time msec = 600/12) MR image of the spine, obtained after administration of gadolinium-based contrast material, shows a soft-tissue mass with heterogeneous enhancement. Note the enhanced rim or periphery and the central area of low signal intensity. Invasion of the surrounding muscle (arrow) was confirmed at microscopic evaluation of a tissue specimen.
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Rhabdomyosarcoma
Rhabdomyosarcomas are high-grade sarcomas characterized by skeletal muscle differentiation. They are usually found in patients younger than 45 years of age, in the abdomen, head, or neck; chest wall involvement is relatively uncommon. Rhabdomyosarcomas in the chest wall typically manifest as rapidly growing masses (Fig 2) and may cause pain and other symptoms due to nerve compression. Bone invasion by a primary tumor occurs in more than 20% of patients. There are several histologic subtypes of rhabdomyosarcoma: embryonal, alveolar, and pleomorphic (7). The alveolar subtype occurs more frequently than the embryonal subtype in the chest wall and extremities, and it has the worst prognosis of all rhabdomyosarcoma subtypes. MR images of pleomorphic and alveolar rhabdomyosarcomas show areas of necrosis with low signal intensity that do not enhance after contrast material administration and that alternate with ringlike areas of high signal intensity and marked enhancement (8). Alveolar rhabdomyosarcomas typically include multiple areas of necrosis. Embryonal rhabdomyosarcomas, which typically occur in children, sometimes extend to the anterior and lower chest wall and involve the mediastinum. In all rhabdomyosarcoma subtypes, as in other soft-tissue tumors, CT and MR imaging allow optimal evaluation of tumor extent and medullary involvement.
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Figure 2. Rhabdomyosarcoma in a 51-year-old woman. Coronal reformatted image of the apex of the left hemithorax from a contrast-enhanced CT study shows a mass that has invaded muscle, fascia, adipose tissue, nerves, and vascular structures (arrows). A = aorta, C = clavicle.
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Vascular Tumors: Angiosarcomas
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Angiosarcomas are malignant endothelial neoplasms characterized by vasoformative architecture. Angiosarcomas frequently manifest as large, painful, and rapidly growing masses and are often mistaken for chronic hematomas. Angiosarcomas occasionally are associated with hemorrhage, anemia, or coagulopathy (9). Chronic lymphedema is the most widely recognized factor predisposing individuals to angiosarcoma (10), but this tumor type also is associated with radiation therapy and chemical exposure. In contrast to malignant cutaneous lesions, which are more often found in the head and neck, angiosarcomas typically originate in the deep soft tissues of the lower extremities (11). In the chest wall, angiosarcomas occur primarily in the breast, most often in association with lymphedema or radiation therapy of breast carcinoma. MR images of angiosarcoma show a heterogeneous mass that sharply enhances after intravenous administration of gadolinium-based contrast material (Fig 3). Feeding vessels often are seen in the periphery of the tumor. Fibrous thickening, soft-tissue nodules, increased attenuation in fatty tissue, and fluid collections around muscle characterize angiosarcoma and other tumor types associated with lymphedema.
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Figure 3. Angiosarcoma in a 67-year-old man. Axial gadolinium-enhanced T1-weighted (600/12) MR image of the apex of the left hemithorax shows an invasive mass with heterogeneous enhancement in the left lateral chest wall. Vascular flow-voids are seen near the surface of the tumor (arrows). V = vertebra.
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Fibrous and Fibrohistiocytic Tumors
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Malignant Fibrous Histiocytoma
MFH, a soft-tissue sarcoma most often found in older adults, rarely occurs in the chest wall. The tumor typically originates in deep fascia or skeletal muscle and only rarely originates in bone, although involvement of adjacent bone is common (12). MFH initially was described as having a histiocytic origin, but histogenesis of this tumor type is now uncertain (13). Storiform-pleomorphic MFH is the most common form, accounting for more than two-thirds of all cases. MFH manifests on CT scans as a nonspecific heterogeneously enhancing mass in muscle and fascia planes (Fig 4). Myxoid MFH is the second most common type, with a characteristic CT appearance of low attenuation in the myxoid matrix at the center of the lesion and nodular peripheral enhancement of the more cellular tumor components. On T1- and T2-weighted MR images, MFH may appear either homogeneous or heterogeneous. On T1-weighted images, most tumors have a signal intensity equal to that of muscle, and on T2-weighted images, they have a signal intensity equal to or greater than that of fat (12). Tumors often show heterogeneous enhancement on MR images obtained with gadolinium-based contrast material.
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Figure 4a. Storiform-pleomorphic malignant fibrous histiocytoma in a 68-year-old woman. (a) Nonenhanced CT scan at the level of the ascending aorta (A) shows a destructive mass with origins in the sternum and extension into the surrounding soft tissue (arrowheads). (b) Photograph of the dissected tumor reveals invasion of the subcutaneous tissue (arrowheads). R = rib.
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Figure 4b. Storiform-pleomorphic malignant fibrous histiocytoma in a 68-year-old woman. (a) Nonenhanced CT scan at the level of the ascending aorta (A) shows a destructive mass with origins in the sternum and extension into the surrounding soft tissue (arrowheads). (b) Photograph of the dissected tumor reveals invasion of the subcutaneous tissue (arrowheads). R = rib.
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Aggressive Fibromatosis
Aggressive fibromatosis or desmoid tumor is an infiltrative lesion with an intermediate proliferative tendency; although not as aggressive as the exuberantly proliferative adult fibrosarcoma, it is more aggressive than infantile or congenital fibrosarcoma. Lesions in aggressive fibromatosis do not metastasize, and they may even undergo spontaneous regression. Their exact pathogenesis is unknown; however, trauma, endocrine disorders, and genetic factors have been implicated (14). Aggressive fibromatosis may occur in Gardner syndrome, but the association is much stronger for fibromatosis in the abdomen than for that in the chest wall. Aggressive fibromatosis is a common neoplastic disease and accounts for 54% of low-grade sarcomas of the chest wall (1). A chest wall site of origin has been reported in 10%–28% of patients, with shoulder involvement being the most common complication (15). Aggressive fibromatosis of the chest wall often affects adolescents and young adults (1,16–19) but also may occur in older patients (Fig 5). CT scans show variable degrees of attenuation and enhancement in accordance with variations in tumor composition. An infiltrative pattern is more common in young patients, whereas a nodular pattern is more frequent in adults. The tumor is usually confined to the musculature and adjacent fascia, but encasement of adjacent nerves and vessels also may occur. Infiltration of overlying subcutaneous tissue is uncommon, and although the lesion may cause pressure erosions on adjacent bones, bone invasion is unusual. On T1-weighted MR images, tumors have signal intensity less than or equal to that of muscle, whereas on T2-weighted images they have mostly intermediate signal intensity, although very low and extremely high signal intensities also have been observed occasionally. Low-signal-intensity areas on T2-weighted images are thought to result from high collagen content. Differences in signal intensity between different tumor components, between asynchronous multicentric tumors, and between primary and recurrent lesions may be caused by a combination of variations in cellular contents, amount of collagen, water content of the extracellular space, and vascularity (16–19).
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Figure 5a. Aggressive fibromatosis in a 38-year-old woman. (a) Coronal reformatted image of the right axilla from a contrast-enhanced multidetector CT study shows a mass (M) inferior to the scapula (S) with invasion of the surrounding musculature (arrows). (b) Photograph of the resected specimen shows a mass (M) of dense trabeculated fibrous tissue with invasion of adjacent structures (arrowheads).
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Figure 5b. Aggressive fibromatosis in a 38-year-old woman. (a) Coronal reformatted image of the right axilla from a contrast-enhanced multidetector CT study shows a mass (M) inferior to the scapula (S) with invasion of the surrounding musculature (arrows). (b) Photograph of the resected specimen shows a mass (M) of dense trabeculated fibrous tissue with invasion of adjacent structures (arrowheads).
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Peripheral Nerve Tumors
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Neuroblastoma and Ganglioneuroblastoma
Thoracic neuroblastomas and ganglioneuroblastomas most often occur in the extraadrenal sympathetic ganglia in the chest wall in children (20–22) (Fig 6). Tumors typically manifest as palpable masses and may or may not be accompanied by pain and other symptoms related to the biochemical activity of the tumor. Neuroblastoma consists primarily of immature neuroblasts, whereas ganglioneuroblastoma contains a variable component of mature glial cells and ganglion cells (20–22). The prognosis is variable and depends on the patient’s age at diagnosis, the stage of disease, and the histologic findings. CT scans of neuroblastoma show ill-defined tumors, commonly with calcification. On MR images, tumors may exhibit heterogeneous and nonspecific signal intensity, although overall low signal intensity is typically observed on T1-weighted images and high signal intensity is seen on T2-weighted images. Areas of necrosis and hemorrhage are frequently present. Intrathecal extension of neuroblastoma is best demonstrated with MR imaging (20).
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Figure 6. Ganglioneuroblastoma in a 6-year-old girl. Axial T2-weighted (6,000/112) MR image at the level of the diaphragm (D) shows a tumor (arrowheads) with heterogeneous high signal intensity extending along the pleural surface.
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Malignant Peripheral Nerve Sheath Tumor
Malignant peripheral nerve sheath tumors, previously known as malignant schwannomas, are neoplasms of nerve sheath origin that both infiltrate locally and metastasize. Considered counterparts of glioblastomas of the central nervous system, these tumors occur sporadically, with approximately equal frequency in men and women except in the presence of type 1 neurofibromatosis (caused by a recessive oncogene), which is associated with a frequency four times greater in men than in women. The mean age of incidence is 42 years, with 80% of cases occurring between the ages of 17 and 70 years (23). In approximately 50% of patients in whom malignant peripheral nerve sheath tumor is diagnosed, an association is found with type 1 neurofibromatosis (23). The tumor usually manifests as a slow-growing mass. Pain is more common in patients with type 1 neurofibromatosis, and the development of pain in a neurofibroma portends malignant transformation. CT scans of malignant peripheral nerve sheath tumors usually show a large heterogeneous mass, occasionally accompanied by bone destruction. MR images show a large invasive mass (Fig 7) located along the course of a peripheral nerve. The internal architecture of the tumor may be heterogeneous and irregular in accordance with the extent of necrosis, hemorrhage, and cellularity (24). Tumors exhibit signal intensity equal to or slightly greater than that of muscle on T1-weighted images. On T2-weighted images, signal intensity is markedly increased. Heterogeneous enhancement is observed after intravenous administration of contrast material (25). Findings of tumor invasion in surrounding fatty tissue or other neighboring structures, as well as bone edema or perilesional edema, can be of help in the diagnosis; however, MR imaging findings in benign plexiform neurofibromas often are similar to those in malignant peripheral nerve sheath tumors. Malignant transformation of neurofibroma may result in the loss of the targetlike appearance of the lesion (a peripheral area of high signal intensity with a central area of low signal intensity) on T2-weighted images.
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Figure 7. Malignant peripheral nerve sheath tumor in a 74-year-old woman. Axial T2-weighted (6,000/112) MR image at the level of the aortic arch (A) shows an ill-defined tumor with invasion of bone, fat, muscle, and fascia (arrowheads).
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Osseous and Cartilaginous Tumors
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Chondrosarcoma
Chondrosarcomas, the most common malignant primary tumors of the chest wall, usually occur in the anterior part of the wall, arising from the costochondral arches or sternum (26). Extraosseous chondrosarcomas are much less common. Nineteen percent of chondrosarcomas occur in the ribs. Most of these are primary lesions, but 10% arise from preexisting benign tumors. Two peak periods of prevalence have been identified—the first, at less than 20 years of age, and the second, at more than 50 years of age. These tumors occur twice as often in men as in women, and they most frequently are found along the upper five ribs, adjacent to costal cartilage (26,27).
Bone destruction, irregular contours, and intratumoral mineralization are characteristic but variable features detected on chest radiographs. The degree and type of calcification may vary; images may show rings and arcs, flocculent or stippled calcification, or dense calcification. CT is more sensitive than radiography and MR imaging for delineation of chondroid matrix calcifications (Figs 8a, 9a). The better-differentiated chondrosarcomas appear on CT scans as well-defined, densely calcified soft-tissue masses. T1-weighted MR images show lobulated masses with signal intensity similar to that of muscle, and T2-weighted MR images show masses with signal intensity equal to or greater than that of fat (Figs 8b, 9b). Enhancement after administration of intravenous contrast material typically is heterogeneous, especially at the periphery (28–30). Myxoid chondrosarcomas do not contain chondroid calcifications or bone formation and may have markedly high signal intensity on T2-weighted images.
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Figure 8a. Chondrosarcoma in a 19-year-old woman. (a) Contrast-enhanced CT scan at the level of the left atrium (A) shows a rib mass with chondroid mineralization (black arrowheads) and invasion of the overlying musculature (white arrowhead). (b) Sagittal T2-weighted (6,000/112) MR image of the lateral chest wall shows a mass arising from the rib (R), with a signal intensity higher than that of intercostal muscle. Areas of low signal intensity (arrowheads) indicate dense mineralization in the tumor.
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Figure 8b. Chondrosarcoma in a 19-year-old woman. (a) Contrast-enhanced CT scan at the level of the left atrium (A) shows a rib mass with chondroid mineralization (black arrowheads) and invasion of the overlying musculature (white arrowhead). (b) Sagittal T2-weighted (6,000/112) MR image of the lateral chest wall shows a mass arising from the rib (R), with a signal intensity higher than that of intercostal muscle. Areas of low signal intensity (arrowheads) indicate dense mineralization in the tumor.
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Figure 9a. Dedifferentiated chondrosarcoma in a 66-year-old man. (a) Contrast-enhanced CT scan at the level of the pulmonary artery (P) shows a mass with peripheral calcification (arrow) arising from the costovertebral joint and expanding into the thoracic cavity. Note the small pleural effusion. (b) Axial T2-weighted (4,500/97.7) MR image at the level of the pulmonary artery shows a tumor with heterogeneous high signal intensity extending into the thoracic cavity and invading the vertebral pedicle (curved arrow). The MR image better depicts the tumor extension in the rib (straight arrow) than does the CT scan. The pleural effusion had increased in size by the time of MR imaging.
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Figure 9b. Dedifferentiated chondrosarcoma in a 66-year-old man. (a) Contrast-enhanced CT scan at the level of the pulmonary artery (P) shows a mass with peripheral calcification (arrow) arising from the costovertebral joint and expanding into the thoracic cavity. Note the small pleural effusion. (b) Axial T2-weighted (4,500/97.7) MR image at the level of the pulmonary artery shows a tumor with heterogeneous high signal intensity extending into the thoracic cavity and invading the vertebral pedicle (curved arrow). The MR image better depicts the tumor extension in the rib (straight arrow) than does the CT scan. The pleural effusion had increased in size by the time of MR imaging.
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Osteosarcoma
Osteosarcomas are malignant mesenchymal neoplasms that rarely occur in the thorax. The rib, scapula, and clavicle are the most frequent sites of origin. Lesions originating in these osseous sites usually manifest in young adults and may be accompanied by extrapleural masses. Extraosseous osteosarcoma (Fig 10) is less common and manifests at a mean age of 50 years. Chest wall osteosarcomas typically manifest clinically as painful masses. Local recurrence and metastatic spread to the lungs and lymph nodes are frequent in osteosarcomas in the chest wall, compared with those in the extremities, and contribute to poor survival. Radiographs typically show calcification or lytic or sclerotic osteoid bone matrix in the mass. An important feature on CT scans is the spatial distribution of areas of mineralization, which is greatest at the center of the lesion and least at the periphery. MR imaging may depict tumor mineralization, which may have a signal intensity higher than that of muscle on T1weighted images. A mixed but predominantly high signal intensity is observed on T2-weighted images. Large cystic components also may be depicted (31). The tumor shows heterogeneous enhancement after administration of intravenous contrast material.
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Figure 10. Osteosarcoma in a 25-year-old woman. Axial gadolinium-enhanced T1-weighted (500/15) MR image shows a large mass (M) with heterogeneous enhancement in the upper left hemithorax. The mass has invaded the posterior chest wall (arrowheads) and filled the thoracic cavity on the left side. V = vertebra.
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Adipose Tissue Tumors: Liposarcomas
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Liposarcomas constitute 15% of all sarcomas and usually arise as painless masses in the lower extremities or the retroperitoneum. Chest wall origin is uncommon, occurring in about 10% of cases. The tumor consists of lipoblasts that vary in configuration from poorly differentiated round cells to mature adipose tissue. Many tumors have a large component of myxoid intercellular material. The CT appearance and MR imaging findings are closely correlated with these gross anatomic and microscopic findings; well-differentiated tumors have characteristics similar to those of mature fat, whereas poorly differentiated liposarcomas, which are more cellular, have characteristics similar to other solid tumors. The differences seen in these tumors at imaging are reflected in their different prognoses.
At CT, the attenuation of liposarcoma is slightly higher than that of normal fat because the tumor contains both fat and soft tissue. The lesions are usually heterogeneous in appearance, reflecting variable cellularity within the tumor. Areas of calcification and ossification may be seen, especially in liposarcomas of the myxoid type. At MR imaging, myxoid liposarcomas usually show moderately high signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Round cell liposarcomas often do not contain a large amount of fat and therefore exhibit a nonspecific heterogeneous appearance, with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images (Fig 11). Dedifferentiated liposarcoma should be suspected if a previously well-differentiated liposarcoma develops areas of high signal intensity on T2-weighted images and low signal intensity on T1-weighted images (Fig 12), and if those areas enhance after intravenous administration of contrast material (32–39).
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Figure 11a. Round cell liposarcoma in a 34-year-old man. (a) Axial T2-weighted (6,000/112) MR image reveals a large mass (M) with heterogeneous but overall high signal intensity that originates from the posterior chest wall, fills the thoracic cavity, and displaces the aortic arch (A). (b) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows atypical round cells in a myxoid background that accounts for the very high signal intensity on the T2-weighted MR image.
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Figure 11b. Round cell liposarcoma in a 34-year-old man. (a) Axial T2-weighted (6,000/112) MR image reveals a large mass (M) with heterogeneous but overall high signal intensity that originates from the posterior chest wall, fills the thoracic cavity, and displaces the aortic arch (A). (b) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) shows atypical round cells in a myxoid background that accounts for the very high signal intensity on the T2-weighted MR image.
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Figure 12. Dedifferentiated liposarcoma in a 56-year-old man. Axial T1-weighted (600/12) MR image of the apex of the left hemithorax shows a mass that originates from the left superior chest wall and has heterogeneous signal intensity including a fat component (arrow) and a larger soft-tissue component. V = vertebra.
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Hematologic Malignancies
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Malignant Lymphoma
Primary malignant lymphomas in the chest wall account for less than 2% of soft-tissue tumors, although secondary involvement of the musculoskeletal system is common in soft-tissue tumors (40) (Fig 13). Extranodal diffuse large B-cell lymphoma, the primary lymphoma type most frequently found in the chest wall, manifests in a multinodular or diffuse infiltrative pattern (41). The disease mainly affects patients in their 50s. An increased incidence has been described in individuals who have undergone either orthopedic surgery with metallic implants or organ transplantation with immunosuppressive treatment and in patients with AIDS. CT scans of these lesions show attenuation similar to that of muscle and diffuse slight enhancement after intravenous injection of contrast material. At MR imaging, tumors manifest as large masses with intermediate signal intensity equivalent to or slightly lower than that of adjacent muscle on T1-weighted images and with high signal intensity on T2-weighted images (42). Infiltration along the neurovascular bundle and extension through the subcutaneous tissues are common.
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Figure 13. Malignant lymphoma in a 62-year-old woman. Coronal T1-weighted (605/20) fat-suppressed MR image at the level of the left atrium (A) shows an infiltrating mass in the chest wall (arrows) with homogeneous enhancement after administration of gadolinium-based contrast material.
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Solitary and Multiple Myeloma
Solitary myeloma and multiple myeloma are plasma cell tumors that manifest, respectively, as a single mass or with diffuse marrow involvement. Solitary myeloma is diagnosed in patients at a mean age of about 50 years, in contrast to multiple myeloma, in which the age range at manifestation is 50–70 years (43) (Fig 14). Solitary myeloma may progress over time to multiple myeloma. Solitary myeloma of bone manifests radiologically as a multicystic expansile mass or purely osteolytic focus without expansion. Extraosseous solitary myeloma, which manifests as a nonspecific soft-tissue mass, progresses less frequently to multiple myeloma (44). Multiple myeloma, the abnormal accumulation of plasma cells in bone marrow, is associated with multiple areas of osteolysis because the plasma cells produce an osteoclast-stimulating factor. Multiple osteolytic lesions with discrete margins are typically detected radiologically in the vertebral column, ribs, or clavicles (Fig 15). Sclerosis generally develops in the osteolytic lesions after pathologic fracture, irradiation, or chemotherapy but occasionally can be seen also in untreated lesions. At MR imaging, tumors show low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Contrast-enhanced MR imaging may be an effective means of monitoring the response to therapy (45).
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Figure 14a. Solitary myeloma in a 69-year-old woman. (a) Nonenhanced CT scan at the level of the pulmonary artery (P) shows a well-defined subpleural mass with reactive bone sclerosis (arrowheads). (b) Photograph of the resected specimen shows a well-demarcated mass (arrows) with minimal bone invasion.
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Figure 14b. Solitary myeloma in a 69-year-old woman. (a) Nonenhanced CT scan at the level of the pulmonary artery (P) shows a well-defined subpleural mass with reactive bone sclerosis (arrowheads). (b) Photograph of the resected specimen shows a well-demarcated mass (arrows) with minimal bone invasion.
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Figure 15. Multiple myeloma in a 59-year-old man. Contrast-enhanced CT scan at the level of the aortic arch (A) shows multiple osteolytic lesions involving the sternum, vertebral body, scapulae, and ribs, and a soft-tissue mass (arrowheads) that originates from a left rib.
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Cutaneous Tumor: Dermatofibrosarcoma Protuberans
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Dermatofibrosarcoma protuberans is a rare malignant tumor of the skin with a high propensity for local invasion and recurrence. It typically occurs in adolescents but also may occur much later in life. The clinical course is characterized by a strong tendency toward local recurrence of the lesion, usually within 3 years after initial treatment. Metastases to the pulmonary and regional lymph nodes have been reported but are rare and usually preceded by multiple local recurrences. Two different types of tumor may occur in this disease: an aggressive fibrosarcomatous variant and a classic variant with a more indolent course. A finding of high-grade fibrosarcomatous change in at least 5% of the lesion indicates the presence of the first variant (46). CT scans in this type show well-defined nodular subcutaneous lesions with attenuation equal to or slightly higher than that of skeletal muscle and with moderate enhancement after intravenous administration of contrast material (Figs 16, 17). MR imaging findings are nonspecific and may include heterogeneous foci of hemorrhage, myxoid change, or necrosis (47).
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Figure 16. Low-grade dermatofibrosarcoma protuberans in a 56-year-old man. Contrast-enhanced CT scan at the level of the aortic arch (A) shows a well-demarcated subcutaneous mass (arrow) without muscle invasion.
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Figure 17. High-grade dermatofibrosarcoma protuberans in a 68-year-old woman. Contrast-enhanced CT scan at the level of the left atrium (A) shows a large heterogeneous mass (arrow) that originates from the anterior chest wall. Invasion of mediastinal structures (arrowheads) suggests malignancy.
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Other Important Tumors
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Ewing Sarcoma
A clinicopathologic entity characterized by malignant small cell tumors that appeared to originate in the soft tissue of the chest wall or the periphery of the lung was first described by Askin et al (48) in 20 children and adolescents. Then known as primitive neuroectodermal tumor, this lesion is now recognized as an aggressive type of Ewing sarcoma. Both tumor types manifest most often in children and young adults and probably develop from embryonal neural crest cells. Both also contain the same balanced reciprocal translocation between chromosomes 11 and 22—that is, t(11;22)(q24;q12). The translocation point has been cloned and is identical in the two tumor types (49,50).
Ewing sarcoma of the chest wall develops either as a solitary mass or as multiple masses with an eccentric growth pattern. Tumors usually occur in the rib, scapula, clavicle, or sternum but occasionally have an extraskeletal site of origin. Expansion of a chest wall tumor may cause the lung to collapse, or the neoplasm may invade the lung. Ewing sarcoma often originates in a paravertebral region and extends through the vertebral foramina. Although tumors generally tend to displace adjacent soft-tissue structures rather than invade or encase them, large tumors may directly infiltrate the surrounding structures. CT scans of Ewing sarcoma typically show a large ill-defined mass with an inhomogeneous appearance caused by extensive cystic degeneration, which may or may not be accompanied by calcification (51). On T1-weighted MR images, tumors generally have signal intensity equal to or greater than that of muscle. Larger tumors appear as heterogeneous masses, frequently with evidence of hemorrhage or necrosis (Fig 18), whereas smaller ones tend to be more homogeneous. On T2-weighted images, the tumors tend to have inhomogeneous high signal intensity. Tumors show marked enhancement after intravenous administration of contrast material (52).
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Figure 18a. Ewing sarcoma in a 15-year-old girl. (a) Axial T1-weighted (600/12) MR image at the level of the diaphragm (D) shows an extraosseous extrapleural mass. A focus of high signal intensity (arrow) indicates intratumoral hemorrhage. (b) Photograph of the resected specimen reveals no bone involvement. A small focus of hemorrhagic degeneration (arrow) corresponds to the area of high signal intensity on the MR image.
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Figure 18b. Ewing sarcoma in a 15-year-old girl. (a) Axial T1-weighted (600/12) MR image at the level of the diaphragm (D) shows an extraosseous extrapleural mass. A focus of high signal intensity (arrow) indicates intratumoral hemorrhage. (b) Photograph of the resected specimen reveals no bone involvement. A small focus of hemorrhagic degeneration (arrow) corresponds to the area of high signal intensity on the MR image.
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Synovial Sarcoma
Synovial sarcomas are rare malignant mesenchymal neoplasms that most often occur near joint capsules, bursae, and tendon sheaths of the extremities. Synovial sarcoma in the chest wall is extremely rare and usually occurs in patients of ages 15–40 years but may also occur later in life. Synovial sarcoma is clinically and morphologically well defined and has been extensively described in the literature; however, its biologic features remain controversial. Specific diagnosis is made by identifying a t(X;18)(p11;q11) translocation in the tumor cells (53). CT scans typically show a soft-tissue mass with attenuation slightly higher than that of muscle and may show infiltration of adjacent structures. Cortical bone erosion or invasion is well depicted at CT, as are intratumoral calcifications, which are noted in 20%–30% of cases (54). On T1-weighted MR images, most tumors show heterogeneous signal intensity that is predominantly equivalent to that of muscle. Small foci of high signal intensity on T1-weighted images, which are present in 45% of cases, indicate hemorrhage. Fluid-fluid levels can be striking and are seen in 15%–25% of patients (55). Findings of hemorrhage and fluid-fluid levels or high signal intensity on any MR image may be associated with a worse prognosis, because these tumors are usually large and extensively invasive of surrounding tissue. On T2-weighted images, marked heterogeneity is the rule, and various degrees of internal septation may be noted (Fig 19). These findings are especially characteristic of large tumors, 85% of which have heterogeneous signal intensity (55,56). A combination of three different signal intensity levels is present on T2-weighted images in 33% of cases: high signal intensity similar to that of fluid, intermediate signal intensity equal to or higher than that of fat, and low signal intensity close to that of fibrous tissue. This triple-signal-intensity pattern on T2-weighted images, when accompanied by small foci of high signal intensity on T1-weighted images, calcifications, and proximity to a joint, may indicate the diagnosis.
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Figure 19a. Synovial sarcoma in a 60-year-old woman. (a) Coronal T2-weighted (6,000/112) MR image shows a large paravertebral mass with heterogeneous signal intensity and numerous internal septa. The tumor has displaced the diaphragm (arrowheads). (b) Photograph of the dissected tumor reveals invasion of the paravertebral muscle (arrowheads) and cystic degeneration and hemorrhage (arrow), which account for the heterogeneous signal intensity observed in the tumor on the MR image.
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Figure 19b. Synovial sarcoma in a 60-year-old woman. (a) Coronal T2-weighted (6,000/112) MR image shows a large paravertebral mass with heterogeneous signal intensity and numerous internal septa. The tumor has displaced the diaphragm (arrowheads). (b) Photograph of the dissected tumor reveals invasion of the paravertebral muscle (arrowheads) and cystic degeneration and hemorrhage (arrow), which account for the heterogeneous signal intensity observed in the tumor on the MR image.
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Proximal-type Epithelioid Sarcoma
Proximal-type epithelioid sarcoma is a distinctive neoplasm that commonly involves soft tissue in the extremities. Although it may occur at any age, the tumor is most often found in adolescents and young adults. Lesions may be subcutaneous or deep seated and usually are attached to tendons, tendon sheaths, or fascial structures (
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Abstract
LEARNING OBJECTIVES
