A 51-year-old right-hand dominant man was evaluated for an enlarging, painless left wrist mass of 2 months duration. The patient reported no recent injury or antecedent trauma and denied any local neurologic symptoms, fevers, chills, or changes in weight.Physical examination revealed a nontender, 3 9 2-cm firm, mobile mass overlying the volar aspect of the left distal ulna. There was no rash or other identifiable overlying skin changes, and the lesion did not transilluminate. The patient had normal strength and ROM, and sensation to light touch was intact in all three nerve distributions. There was a negative Tinel's sign and the mass was nonpulsatile with a normal vascular examination.AP and lateral views of the left wrist ( Fig. 1) and MRI of the wrist (Fig. 2) were obtained.