Multiple keratoacanthomas, giant keratoacanthoma and keratoacanthoma centrifugum marginatum: development in a single patient and treatment with oral isotretinoin.

A 78-year-old man is described, who over 18 years developed three different types of keratoacanthoma: multiple keratoacanthomas, keratoacanthoma centrifugum marginatum and giant keratoacanthoma. Histological examination of the different neoplasms showed similar changes, all typical of a keratoacanthoma. In situ hybridisation revealed no human papilloma virus in the tumours. Complete examination showed no associated internal malignancy. After repeated surgical treatment oral isotretinoin treatment was administered (1 mg/kg per day). This treatment produced clearing of existing keratoacanthomas and, during a period of 2 months, further keratoacanthoma formation was completely suppressed. Treatment was stopped after 3 months by the patient because of side-effects. Numerous keratoacanthomas developed during the following 6 weeks.