KERATOACANTHOMA

The keratoacanthoma (KA) is a rapidly growing tumor, usually of the sun-exposed skin that mimics a squamous cell carcinoma (SCC). In fact, the distinction between keratoacanthoma and squamous cell carcinoma, both clinically and histologically, is often difficult.

• The classic KA resolves spontaneously but rarely lesions may become huge by unrestricted growth.
• Chronic UV exposure is a predisposing factor and the patient should be examined for other nonmelanoma skin cancers. HPV DNA is found in a small percentage of lesions.
• Variants include multiple KAs of Grzybowski, of Ferguson-Smith as well and the vary large keratoacanthoma centrifugum marginatum.

A rapidly growing nodule that develops a central keratotic core in the sun-exposed area of an elderly person is characteristic. The hands and arms as well as the head and neck are commonly affected. The squamous cell carcinoma may present in a very similar manner as a red-white nodule, often with a hyperkeratotic core. As a rule, the SCC is slower growing than the KA--appearing over several months. Note that the basal cell carcinoma is usually pearly, translucent, and without any keratotic core.

Keratoacanthoma vs. Squamous Cell Carcinoma

Many studies have been performed to distinguish KA from SCC. Most of these rely on histologic criteria, although various immunohistochemical markers have been added to the toolbox. Unfortunately, many tumors still defy classification. Indeed, some even consider the keratoacanthoma a type of squamous cell carcinoma.

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