Synovitis, Pigmented Villonodular

Diffuse outgrowth arising from the SYNOVIAL MEMBRANE; SYNOVIAL BURSA; or TENDON sheath around the joint cavity, with extension to surrounding soft tissue. It is characterized by pigmented HEMOSIDERIN-containing MACROPHAGES; FOAM CELLS; and multinucleated GIANT CELLS. It usually occurs in the hands and feet, and around large joints, such as in the ankle and knee joints.