Giant cell tumor of a tendon sheath mimicking an axillary lymph node.

A giant cell tumor of the tendon sheath (GCTTS) is 1 of the most common soft-tissue tumors of the hand and wrist, while the 2nd most frequent site is the ankle-foot complex. Although various solid tumors can develop in the axilla, GCTTS has not yet been reported. We describe the sonographic appearance of GCTTS in the axilla.