Definition

A type of rare tumor that forms in the synovium (tissue that lines the joints), the tendon sheath (tissue that covers the tendons), or the bursa (a fluid-filled sac between bones, tendons, and muscles). These tumors cause the affected synovium, tendon sheath, or bursa to thicken and overgrow. TGCTs can occur in any joint. Although TGCTs are not cancer, they can grow and cause damage to surrounding tissues or structures. Symptoms may include reduced movement or pain in the affected joint and a locking or catching sensation when moving the joint. TGCTs usually occur in young and middle-aged adults. Also called tenosynovial giant cell tumor.