The purpose of this study is to evaluate the radiologic findings of the extraosseous Ewing's sarcoma.

Six patients with pathologically confirmed extraosseous Ewing's sarcoma were retrospectively reviewed. Patients included two men and four women with an average age of 21.5 years (age range 9-48 years). Plain radiographs (six patients), magnetic resonance (MR) images (five patients), computed tomographic (CT) scans (three patients) and whole body scintigraphy (two patients) were reviewed and analyzed. Images were evaluated with regard to lesion location, size, margin, muscle or bone involvement and intrinsic imaging characteristics on CT and MRI.

The tumors were located in the thigh (three patients), back (two patients) and upper arm (one patient). The tumors ranged in size from 2.3 cm to 7.5 cm (mean, 5.2 cm), were mainly well circumscribed and showed no evidence of calcification prior to treatment. Margins were well defined in four out of the six patients. Four patients had subcutaneous lesions and the other two patients had intramuscular lesions. Muscle (two patients) and bone invasion (one patient) were present. The masses were heterogenous low signal intensity on T1 weighted images and heterogeneous high signal intensity on T2 weighted images compared with muscle. Heterogeneous enhancement within the lesion was observed in all patients on CT and MRI. Whole body scintigraphy using Tc-99 m MIBI showed increased uptake in the masses of two patients.

Extraosseous Ewing's sarcomas were frequently seen as a well-circumscribed ovoid mass with nonspecific findings on CT and MRI. Despite being a relative rare tumor, it should be included in the differential diagnosis of a non-calcified soft-tissue mass, especially in subcutaneous tissue.