The Keratoacanthoma: A Review

The keratoacanthoma (KA) was a common tumor found primarily 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 smooth nodule, developing into a dome-shaped tumor with a keratotic core, and eventually degenerating. While typically appearing as a solitary lesion, multiple tumors and various morphologic and syndromic variants, such as in Torre syndrome, were observed. KA was believed to originate from hair follicle cells, though its exact cause was unclear, with factors like ultraviolet light, viruses, and chemicals being considered. Histologically, KA resembled cutaneous squamous cell carcinoma, but its architecture usually allowed for differentiation.