Subungual exostosis of the thumb.

A 19-year-old girl presented with painful raised skin lesions over the right thumb for the past one year that had ulcerated over the last one month. On examination, a lobulated nodule of bony-hard consistency, measuring around 2 cm was present over the lateral aspect of the tip of the right thumb. The lesion was tender and the overlying skin showed superficial erosions. Roentgenogram of the hand showed mature bone projecting from the distal end of the terminal phalanx of the right thumb forming a "Y"-like bifurcation. Histology from a bit of excised tissue from the lesion (thumb) showed evidence of mature trabecular bone with a fibrocartilaginous cap in the deep dermis. There was no evidence of malignant change on histology. Local excision of the entire lesion was done and there has been no recurrence till date.