Giant cell tumor of the tendon sheath are the second most common tumors of the hand often referred to as xanthoma. Histologically these tumors are composed of multinucleated giant cells, polyhedral histiocytes, fibrosis and hemosiderin deposits. Marginal excision of giant celltumor of the tendon sheath is the treatment of choice. We present a case of Xanthoma of flexorpollicis longus tendon that presented as single enlarging mass in volar aspect of left thumb.After clinical diagnosis work up is done with ultrasound, FNAC and excision biopsy