Synovial sarcoma

Synovial sarcoma, also known as malignant synovioma, is a rare form of cancer that occurs in the soft tissues of the body. Primary synovial sarcomas are most common in the soft tissue near the large joints of the arm and leg, but has been found in most human tissues and organs, including the brain, prostate, and heart. 

Synovial sarcoma usually presents with an otherwise asymptomatic swelling or mass, although general symptoms may be reported such as fatigue. Symptoms vary based on tumor location: 

The mainstay of treatment for synovial sarcoma is surgery.