Synovial sarcoma

A synovial sarcoma (also known as malignant synovioma) is a rare form of cancer which occurs primarily in the extremities of the arms or legs, often in proximity to joint capsules and tendon sheaths. It is a type of soft-tissue sarcoma. The name "synovial sarcoma" was coined early in the 20th century, as some researchers thought that the microscopic similarity of some tumors to synovium, and its propensity to arise adjacent to joints, indicated a synovial origin; however, the actual cells from which the tumor develops are unknown and not necessarily synovial. Primary synovial sarcomas are most common in the soft tissue near the large joints of the arm and leg but have been documented in most human tissues and organs, including the brain, prostate, and heart. Synovial sarcoma occurs in about 1–2 per 1,000,000 people a year. They occur most commonly in the third decade of life, with males being affected more often than females (ratio around 1.2:1).