A large thumb mass.

A 31-year-old man presented with a 5-year history of a spontaneously occurring soft tissue mass on the palmar aspect of his left non dominant thumb. Over 5 months he was having progressive difficulty flexing at the interphalangeal joint. Magnetic resonance imaging demonstrated an heterogeneously enhancing soft tissue mass likely to be either a peripheral fibromatosis or giant cell tumour of the flexor tendon (Figure 1). Intraoperatively a large neuroma in continuity with the ulnar digital nerve was found and debulked (Figure 2). The diagnosis was confirmed histologically.