A keratoacanthoma is a relatively common low-grade malignancy that rapidly appears in elderly, light-skinned individuals. It is more common with individuals having an increased degree of sun exposure and is often found at sites of previous injury or trauma. It can be associated with internal malignancy as in the case of Muir-Torre syndrome and keratoacanthoma visceral carcinoma syndrome (KAVCS). Clinically, and even more so microscopically, KAs resemble squamous cell carcinoma (SCC). There are four types of KAs: solitary, multiple, eruptive, and keratoacanthoma centrifugum marginatum.

Lesions typically are solitary and begin as firm, roundish, skin-colored or reddish bumps, that rapidly progress to dome-shaped nodules with a smooth shiny surface and a central crateriform ulceration or keratin plug that may project like a horn. Most KAs occur on sun-exposed skin and typically arise on the hands, arms, neck and face. The feature of this disease is the rapid growth over a few weeks, followed by a stationary period for another few weeks, and finally spontaneous involution over another few weeks, frequently healing with scarring.

Although KAs are spontaneously regressing growths, treatment is indicated. KAs cannot always be distinguished from squamous cell carcinomas and there is a chance of scarring from spontaneous involution. Treatment of KA is primarily surgical. Systemic retinoids, such as isotretinoin, are a consideration for patients with lesions too numerous for surgical intervention. KAs are radiosensitive and respond well to low doses of
radiation. Radiation therapy may be useful in selected patients with large tumors in whom resection will result in cosmetic deformity or for tumors that have recurred following attempted excisional surgery. Other options include intralesional steroid injections, cryotherapy and electrosurgical methods.

James W.D., Berger T.G., Elston D.M. Andrews’ Diseases of the Skin. 10th ed. Philadelphia: Elsevier Inc, 2006, pp.643-645.
Pattee S.F., Silvis N.G. Keratoacanthoma developing in sites of previous trauma: A report of two cases and review of the literature. J Am Acad Dermatol 2003; 48(2): 535-538.

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Lela Lankerani, D.O.
Department of Dermatology
Philadelphia College of Osteopathic Medicine/Frankford Hospital
Philadelphia, Pennsylvannia.

Stephen M. Purcell, D.O., F.A.O.C.D.
Professor and Chairman of the Department of Dermatology
Philadelphia College of Osteopathic Medicine
Philadelphia, Pennsylvannia