Keratoacanthoma observed.

Conventional advice for managing suspected keratoacanthoma is total excision because of concern that the lesion may be a squamous cell carcinoma and histological differentiation of the two lesions is difficult. Only isolated cases have been published where lesions have been observed, with photographic documentation, to spontaneous resolution. Over 11 years (1992-2002) the author made a primary clinical diagnosis of solitary keratoacanthoma in 19 patients based upon the history and lesion appearance. Two thigh skin graft donor site lesions, and one on the nose and one on the lower lip were excised when there was concern about their growth pattern. A fifth patient was not content to be observed and had the lesion curetted by an oncologist. The remaining 14 patients had observed lesions photographed sequentially until resolution. The commonest single site affected was the hand (five cases). The mean age was 65 years (42-86 years). The mean duration of the lesion at presentation was 9 weeks (4-28 weeks), and the mean time to resolution from appearance was 27 weeks (12-64 weeks). Mean follow-up after resolution was 3 years 5 months (range 9 months-8 years). No recurrences occurred. No scar revisions were necessary. Claims that resolved keratoacanthomas leave poor quality scars that may need surgical revision, were not confirmed in this illustrated series which is the largest published to date. The principles of observational management are outlined and the natural history of the condition and patterns of spontaneous resolution described.