Synovial sarcoma is a malignant tumor of the soft tissues, usually around joints.
Under the microscope the tumor resembles synovial tissue (the lining tissue of joints). Synovial tissue is found around the tendons (bands of fiber that connect muscle to bone), and can form bursa (fluid filled cushioning pouches or sacs found in spaces between tendons, ligaments and bones) found in the area of joints.
This condition tends to occur in adolescents and young adults and affects more males than females. The most common location of origin is the thigh near the knee, but synovial sarcoma can also occur near other joints, mainly in the arms and legs.
Despite its name, it seldom arises within a joint.