Subungual keratoacanthoma. Report of a case and review of the literature.

Subungual keratoacanthoma (SUKA) is an uncommon and clinically distinctive tumor of the nail bed. It can easily be confused with well-differentiated subungual squamous cell carcinoma. Distinguishing features of SUKA include pain, rapid growth, and early underlying bony destruction. Unlike keratoacanthomas arising from sun-exposed skin, SUKAs seldom resolve spontaneously and are more locally destructive. Of 18 cases reported in the literature, five patients have developed recurrent disease, all within five months of the initial surgery. We describe a patient with SUKA initially treated by curettage followed two days later by a conservative amputation that revealed conspicuous residual keratoacanthoma. The deep, burrowing tendency of SUKA and the intimate association with underlying bone may explain the reported tendency for recurrence after curettage.