Epithelioid sarcoma and synovial sarcoma in the same knee.

A patient who had had a synovial sarcoma removed from the soft tissues adjacent to his knee subsequently developed an epithelioid sarcoma on the opposite side of the same joint. The epithelioid sarcoma metastasized to lymph nodes, invaded blood vessels and produced death 16 years after it was first discovered. The unique association of these two tumors may be an interesting coincidence or may have some relevance to the histogenesis of epithelioid sarcoma.