Contribution of magnetic resonance imaging to the diagnosis of extraskeletal Ewing's sarcoma.

A case of extraskeletal Ewing's sarcoma presenting as a large gluteal mass is reported. This is a rare tumor with a frequently grim prognosis. Although the definitive diagnosis requires histological examination, magnetic resonance imaging is useful for determining the location of the tumor, evaluating its spread, and eliminating skeletal Ewing's sarcoma by establishing the integrity of the neighboring bone marrow. The tumor is seen on T1-weighted images as low signal with heterogeneous postgadolinium enhancement. Signal intensity on T2-weighted images is variable. In the case reported here, combination chemotherapy with external beam radiation therapy was ineffective, and the patient died 12 months after the diagnosis.