Subungual Giant Cell Tumor of the Tendon Sheath: An Unusual Location.

Giant cell tumors of tendon sheath (GCTTS), also known as synovialomas, are benign tumors that originate from the fibrous sheath, or soft tissue, that surround tendons. These tumors predominantly present on the hand, but can present in the wrist, ankle, knee, elbow, or hip. The classic presentation of GCTTS is a painless, firm, slow growing mass present for weeks to months. The pathogenesis of GCTTS remains unknown. Histopathological examination of the tumor is required to confirm the diagnosis. The preferred treatment is surgical excision with long-term follow up. To our knowledge, this is the third reported case of GCTTS originating in the subunguium and the first reported case of GCTTS in the subunguium of the toe.