Subungual exostosis is not a true tumor but a proliferation of normal bone or calcified cartilaginous remains arising in the distal phalanx. Subungual exostosis is equally common in both sexes and usually presents as a solitary lesion at a median age of 26. It most commonly affects the great toenail (80% of cases), but involvement of other toenails or, less commonly, the fingernails may occur. The right great toenail is more commonly affected than the left great toenail, presumably due to trauma. The proliferation usually elevates the nail plate, mostly at the distolateral edge, sometimes mimicking a subungual wart. The nail plate may be progressively destroyed. Half of cases are painless, but if the exostosis is large enough, tenderness may be a feature.