Extraskeletal Ewing sarcoma

Case contributed by Brett Pearson
Diagnosis certain


Right knee mass

Patient Data

Age: 30 years
Gender: Female

Plain film shows a soft tissue mass within the posteromedial soft tissues at the level of the metadiaphysis of the distal femur. There is no evidence of bony involvement.


Popliteal fossa-centered mass with extension medially at the level of the medial femoral condyle. Medial aspect involves portions of the medial retinaculum as well as the vastus medialis muscle. The proximal medial collateral ligament complex as well as the medial head of the gastrocnemius are involved with the lesion. Part of the mass is inseparable from underlying periosteum in the posterior medial femoral epicondylar region.

Patchy osteopenia of the osseous structures, likely secondary to disuse. Small knee effusion is present.


Core biopsy taken under CT guidance.

A large soft tissue tumor is present in the posteromedial region about the knee. There are areas of hypoattenuation mixed with attenuation similar to muscle.

Case Discussion

Posteromedial distal thigh mass which was path-proven to be an extraskeletal Ewing sarcoma.

Case courtesy of Dr. Matt Skalski and Dr. George Matcuk.

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