The Keratoacanthoma: A Review

The keratoacanthoma (KA) was a relatively common tumor that typically appeared on sun-exposed areas of light-skinned, middle-aged, and older individuals. It was considered an aborted form of squamous cell carcinoma, rarely progressing into a more severe form. The tumor evolved rapidly through stages: starting as a firm nodule, developing into a dome-shaped tumor with a keratotic core, and eventually degenerating. While usually solitary, multiple KAs could occur, and they were associated with various morphologic and syndromic variants, such as Torre syndrome. The tumor likely originated from hair follicle cells, though its exact cause was unclear, with factors like ultraviolet light, viruses, and chemicals being considered. Histologically, KAs resembled cutaneous squamous cell carcinomas, but their architecture typically allowed for differentiation.