Intraarticular epithelioid sarcoma.

A case of an intraarticular epithelioid sarcoma is presented. The patient was a 35 year old man who presented with a 10 months history of a chronic monoarthritis. The MRI showed a diffuse lesion involving the synovial membrane of the knee. There was a marked increased signal on T2 weighted images. Most epithelioid sarcomas involve the subcutaneous tissues of the hands or feet. This presentation is unusual and this entity should be considered in the differential diagnosis of an intraarticular proliferative process.