What causes keratoacanthoma?
Past sun exposure certainly plays a role. It appears that keratoacanthomas arise from a single hair follicle as they are only seen on hair-bearing skin, not on the palms, for instance. A minor injury seems to be required to trigger off a keratoacanthoma but this is often either not apparent or unremembered by the patient. Cells start multiplying in the hair follicle and the cell mass grows into a keratoacanthoma. Some keratoacanthomas appear to be related to infection with human papilloma virus, the cause of warts. Untreated, a true keratoacanthoma will go on growing for several months, reach a maximum size then self-destruct over several more months. Unfortunately a keratoacanthoma can look exactly like a true skin cancer, a squamous cell carcinoma (SCC), or less commonly like a basal cell carcinoma (BCC).
