A recurrent lump on the hand

A 32-year-old male presented with a 6-month history of a slowly expanding painful mass on the radial aspect of his right middle finger. The mass measured 1.5 x 1.0 cm with no irregularities in the overlying skin, neurovascular status, or joint range of motion. Radiographs were interpreted as showing an exostosis or osteochondroma. The lesion was resected but recurred one year later. A clinical photograph and plain x-ray are shown (Figure 1).