Subungual keratoacanthoma.

The subungual keratoacanthoma is a benign neoplasm which simulates and must be differentiated from squamous cell carcinoma. Subungual keratoacanthomas are rapidly growing tumors, causing bone destruction which usually heal spontaneously. The lesion most often presents as a painful, enlarging mass in middle-aged Caucasian patients. Radiographic examination demonstrates a lytic cup-shaped erosion of the underlying distal phalanx. It is essential to recognize keratoacanthoma and separate it from squamous cell carcinoma, both for prognostic and therapeutic reasons. We present two cases of proven subungual keratoacanthoma and discuss their radiographic and histologic characteristics, as well as the current treatment alternatives for this entity.