Giant cell tumor of tendon sheath.

The giant cell tumor of tendon sheath is a benign histiocytic proliferation of the articular and peritendinous synovial tissue that has only rarely been reported in the dermatologic literature. The lesion manifests as a firm 1 to 3 cm nodule most frequently occurring on the fingers, hands, and wrists, where it is attached to the tendon sheath. Its histopathologic appearance is characterized by the presence of multinucleate giant cells.