Ewing's Sarcoma of the Chest

Eric Richard Handley, MD - Case Coordinator
Marc J Lee, MD - Radiology Discussion
Michael W Bennett, MD - Pathology Discussion
John Anthony Carrino, MD - Attending Radiologist
Steven E Seltzer, MD - Attending Radiologist
Pablo R Ros, MD, MPH - Attending Radiologist

September 8, 2003

Presentation

Imaging Findings

Posteroanterior and lateral radiographs show an opacity over the left peripheral aspect of the hemithorax. The lesion appears to be extraparenchymal. The lateral aspect of the 5th rib on the left side is not well visualized, suggesting erosion. The lungs are clear.

The CT image shows a soft tissue mass that has obtuse margins in relation to the chest wall. On a series of images, it is clear that the lesion directly affects the posterior rib. There is visible thinning of the cortex.

Differential Diagnosis

The CT images support the likelihood that this is a mass of the chest wall, rather than of the lung parenchyma.

Diagnosis

Discussion

The gross specimen includes portions of the fourth through seventh ribs from the left side, a lung wedge, and the mass. Radiographs of the specimen illustrate the destruction of the sixth rib. The cross-sectional images show the tumor replacing the missing rib. The tumor is focally necrotic and cystic. It has a bubbly, glistening, transparent appearance. Low-power microscopy demonstrates that the tumor is composed of small, round, blue cells with indistinct borders. At higher power, the cytoplasm that surrounds the cells is shown to be clear (filled with glycogen); it is still difficult to discern cell borders. There is some mitotic activity (up to 3/10 HPF [high-power field]). All of the resection borders were free of tumor.

Radiology Discussion:

Overall, chest wall tumors are rare. They can originate in any of the chest wall tissues: bone, cartilage, muscle, fat, fibrous connective tissue, nerves, and vessels (blood or lymphatic). In adults, the most common benign chest wall tumors are lipoma and osteochondroma and the most common malignant chest wall tumors are fibrosarcoma and malignant fibrous histiocytoma (MFH). In children, the most common primary chest wall malignancies are peripheral neuroectodermal tumors (PNET)/Askin tumors, rhabdomyosarcoma, and Ewing's sarcoma. Plain radiographs typically show a soft tissue mass along chest wall/pleura; rib changes confirm extrapleural involvement. Computed tomography (CT) and magnetic resonance imaging (MRI) are complementary for evaluating the extent and metastases of these tumors. CT is best suited for showing destruction of bone and the presence of small calcifications, and for guiding biopsy. MRI can illustrate marrow or intraspinal involvement. The differential diagnosis for a chest wall tumor is shown in the following table:

Differential Diagnosis Note: Primary bone lesions are listed in the upper section of the table and the extraosseus lesions are in the lower section.
Benign	Malignant
Osteochondroma (most common benign in adults) Osteoblastoma Enchondroma Osteoid osteoma Fibrous dysplasia (most common non-neoplastic tumor) Langerhans' cell histiocytosis (LCH - peds) Paget's Aneurysmal bone cyst (ABC) Giant Cell Tumor	Ewing's Sarcoma (most common primary pediatric) Chondrosarcoma: chondroid matrix Osteosarcoma Myeloma/solitary plasmacytoma Mets
Lymphangioma Hemangioma: Soft tissue mass, phleboliths, may contain fat Neurogenic: High T2 Lipoma: Fatty Desmoid	Fibrosarcoma MFH: calcification uncommon Liposarcoma: nonfatty elements Rhabdomyosarcoma Synovial sarcoma: juxtaarticular, fluid-fluid levels on MR Lymphoma PNET/Askin tumor (peds)

Ewing’s sarcoma is named for James Ewing (1866-1943), the American pathologist who first described it. It is a malignant tumor composed of small round cells. It originates in the bone and is characterized by the translocation of chromosomes 11 and 22. Approximately 15% of all cases of Ewing’s sarcoma arise in the chest wall, most commonly from a rib (less often from the scapula). The peak incidence occurs between the ages of 10 and 15 years; it is rare in children under 5 years and adults over 30 years. There is a slight male:female predominance (1.6:1). Patients typically present with a painful mass. Fever and malaise are also common symptoms, so it can be difficult to differentiate from osteomyelitis.

The general radiologic appearance of Ewing’s sarcoma is a mass in the chest wall accompanied by destruction of the bone. Ewing’s sarcoma is rarely extraosseus, though this can occur in older patients. Although bone involvement is an important characteristic, the soft tissue components may be much more extensive than the bony component. It will not exhibit matrix calcification. When small, the appearance is typically homogeneous; larger tumors are generally heterogeneous. The femur is the most common site for this tumor, followed by the pelvis, ribs, tibia, humerus, and scapula. Ewing’s sarcoma is treated initially with chemotherapy, followed by surgical resection with or without radiation therapy. This malignant tumor is associated with a high rate of metastasis (75% of cases) and local recurrence. The overall 5-year survival rate is 50%.

References

Gladish GW, Sabloff BM, Munden RF, et al. (2002). Primary Thoracic Sarcomas. Radiographics; 22:621-637.

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