Synovial sarcoma is a rare type of cancer that tends to arise near large joints, particularly the knee, in young adults. Despite its name, it typically doesn't affect the interior of joints, where synovial tissue and fluid are located.
The first sign of trouble is usually a deep-seated lump that may be tender or painful. Synovial sarcoma generally grows slowly. While these tumors can occur in young children, they generally develop in people between the ages of 15 and 40.
While synovial sarcoma can occur almost anywhere in the body, the most common locations are in the legs, arms and throat.