[Subungual keratoacanthoma].

Subungual keratoacanthoma is a very rare condition that varies in its clinical presentation from keratoacanthoma in other localizations. It is a painful lesion that fails to regress spontaneously and shows more vertical growth. On X-ray examination destruction of the underlying bone, caused by pressure, can be seen. It may be difficult to distinguish subungual keratoacanthoma from other subungual tumors, especially squamous cell carcinoma; therefore clinical and histological data should be taken into consideration.