ACR Codes: 68.3255
: Ewing sarcomas are is the most common primary skeletal tumor of the thoracic cage. They are associated with a chromosome 22 translocation and are composed of small round cells. Because Ewing sarcomas can appear radiographically and histologically to PNET (primitive neuroectodermal tumor), cytoplasmic glycogen is evaluated for periodic acid–Schiff staining, a feature seen in Ewing sarcoma but not PNETs. Fifteen percent of all Ewing sarcomas arise primarily in the chest wall, usually from a rib or, less frequently, the scapula. Ewing sarcomas have a male predominance of 1.6:1, typically occur in children or young adults, and are the most common tumor of the chest wall in this age group. Most patients (90%) present with a painful chest wall mass. Fever and malaise are common associated systemic manifestations. The characteristic radiologic manifestation is a chest wall mass associated with bone destruction. However, Ewing sarcomas occasionally manifest as a large mass with only a small component of bone involvement. At CT, the attenuation of the mass is usually homogeneous when small
and heterogeneous when large. Ewing sarcomas are rarely extraosseous in origin, usually in older patients (mean age 20 years), and manifest as well-circumscribed, noncalcified masses in the thorax, more frequently in a paravertebral location. Involvement of bone marrow, the hallmark of an osseous origin, is typically absent at CT or MR imaging in these extraosseous tumors.
Treatment is initially chemotherapy, usually followed by resection with or without radiation therapy. Overall 5- and 10-year survival rates are about 50%. The prognosis is affected by the development of metastases, which occurs in about 75% of patients; the 5-year survival with metastases is less than 30%, whereas survival without metastases approaches 100%. The mass typically has high signal intensity on T1-weighted images and intermediate or high signal intensity on T2-weighted images. Treatment consists of resection, augmented by chemotherapy and radiation therapy. The overall survival is less than 40% at 2 years. Poor prognostic factors include metastases at diagnosis and inability to completely resect the mass.
Reference(s): 1. Gregory W. Gladish et al. Primary Thoracic Sarcomas. RadioGraphics 2002; 22:621–637
2. Kirks DR et al. Pratical Pediatric Imaging, 3rd ed. Philadelphia. Lippincott-Raven, 1998.
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