Neoplasms of the hand are not common. Giant cell tumor of tendon sheath (GCTTS) is the most common primary tumor of the hand. Many different theories have recently been proposed as to whether GCTTS is a neoplasm or a localized reactive process. We believe the evidence supports a neoplastic origin. Although the origin is still not proved, the presentation, diagnosis, and treatment of GCTTS have been clear for a long time.