Subungual exostosis.

Subungual exostosis is an uncommon bony tumor of the distal phalanx most often seen on the hallux. Although this lesion is completely benign, it must be distinguished from a number of other subungual tumors, both benign and malignant. Radiography of the digit is a noninvasive test that should be part of the initial workup whenever subungual exostosis is in the differential diagnosis. Once identified, surgical removal of the exostosis generally is both effective and well tolerated. We present a case of subungual exostosis that was discovered incidentally during a full-body skin examination. We also review the pertinent clinical and histopathologic findings, diagnosis, and treatment of this entity.