Keratoacanthoma

Condition

A rapidly evolving tumour of keratinocytes occurring on sun-exposed skin. Can affect anyone, more common with significant sun exposure history.

History and examination

Rapidly growing lesion arising over a few weeks, then remaining static before spontaneously resolving after about 4–6 months (though this is not a reason to withhold treatment — see Management). Examination shows a raised crater with a central keratin plug; classic size is 1–2 cm (giant variants exist).

Investigations

Consider biopsy prior to excision.

Management

Current guideline recommendation is early excision rather than waiting for spontaneous resolution, relying on a correct clinical diagnosis — a 4 mm margin is standard. If clinically certain of the diagnosis, curettage/diathermy is an option. Treat as an SCC (i.e. by excision) if located on the lip or ear.