Giant synovial cyst of the shoulder presenting as a chest wall mass.

Synovial cysts are most frequently found about the knee. Less commonly they have been described at the shoulder, elbow, ankle, and hip joints. Synovial cysts of the shoulder are associated with rheumatoid arthritis, osteoarthritis, chronic steroid use, Charcot joint disease, and long-standing rotator cuff tears. Although often asymptomatic, patients may present complaining of pain, loss of joint motion, or presence of an unexplained mass. The authors present the case of an elderly man with a very large synovial cyst presenting as an anterior chest wall mass.