musculoskeletal and connective tissue disorders
Joint Tumors
Introduction
Tumors rarely affect joints, unless by direct extension of an adjacent bone or soft tissue tumor. However, 2 conditions—synovial chondromatosis and tenosynovial giant cell tumor (pigmented villonodular synovitis)—occur in the lining (synovium) of joints. These conditions are benign but locally aggressive. Both usually affect one joint, most often the knee and second most often the hip, and can cause pain and effusion. Both are treated by open synovectomy and, for synovial chondromatosis, removal of any intra-articular bodies and metaplastic synovium. There is a malignant soft tissue tumor called synovial sarcoma that arises in different types of soft tissue but is not of synovial origin and seldom occurs inside of a joint. It is a monomorphic blue spindle cell soft tissue cancer with variable degree of epithelial differentiation characterized by the specific SS18-SSX/1/2/4 fusion gene but is often biphasic with both spindle cell and glandular–like components. The term applied to the tumor as "synovial" many decades ago is a misnomer. (See also Overview of Bone and Joint Tumors .) 