Large keratoacanthomas in difficult locations treated with intralesional 5-fluorouracil.

Keratoacanthoma is a benign tumor; however, it may cause massive destruction of normal tissue during its rapid growth phase. Intralesional 5-fluorouracil (5-FU) has been shown to be an effective treatment for keratoacanthoma. We have successfully treated five patients with large keratoacanthomas in difficult locations. There have been no recurrences during follow-up periods ranging from 18 to 45 months. Intralesional 5-FU may be ineffective for keratoacanthomas that are not rapidly proliferating.