Keratoacanthoma (KA) is a special lesion, a pseudocancer, occurring as an isolated nodule usually on the face. It presents as a dome-shaped nodule with a central keratinous plug that mimics squamous cell carcinoma. Unique features are its rapid growth rate, much faster than that of a squamous cell carcinoma, and also its spontaneous remission over a period of several months. Still, in every solitary KA, tissue must be obtained to rule out squamous cell carcinoma.
Causes of 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.
Sometimes minor trauma to the skin occurs before the development of a keratoacanthoma.
Symptoms of Keratoacanthoma
Keratoacanthomas begin as small pimple-like bumps on the skin. The center of the growth is crater-like and solid. However, keratoacanthomas grow very quickly, and can be over 2.5 cm (1 in.) wide within one to two months. Keratoacanthomas usually appear on areas of the skin that are most exposed to the sun, such as the back of the hand, the forearm, and the face. They usually shrink within six months, which pushes out the center plug of keratin and may leave behind a depressed scar.
Diagnosis
Clinical findings confirmed by dermatopathologic findings.
Treatment
Surgery Surgical excision is recommended in that KA cannot always be distinguished from SCC on clinical findings.
Multiple KAs Systemic retinoids and methotrexate have been used.
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