Keratoacanthoma (KA) is a common low-grade (unlikely to metastasize or invade) rapidly-growing skin tumour that is believed to originate from the hair follicle (pilosebaceous unit) and can resemble squamous cell carcinoma.

[1][2] The defining characteristic of a keratoacanthoma is that it is dome-shaped, symmetrical, surrounded by a smooth wall of inflamed skin, and capped with keratin scales and debris.

It grows rapidly, reaching a large size within days or weeks, and if untreated for months will almost always starve itself of nourishment, necrose (die), slough, and heal with scarring.

[5][6][7][8] Frequently reported and reclassified over the last century, keratoacanthoma can be divided into various subtypes and despite being considered benign, their unpredictable behaviour has warranted the same attention as with squamous cell carcinoma.

A number of causes have been suggested including ultraviolet light, chemical carcinogens, recent injury to the skin, immunosuppression and genetic predisposition.

[13] Keratoacanthomas presents as a fleshy, elevated and nodular lesion with an irregular crater shape and a characteristic central hyperkeratotic core.