Keratoacanthoma of the lip: A case report with emphasis on histogenesis.

Keratoacanthoma (KA) is a benign epithelial tumor which presents clinically as a proliferating dome-shaped keratin-filled crater. The lesion occurs predominantly upon sun-exposed areas of the body and is known to arise from hair follicle. Actinic rays are a major contributing factor in the etiology. It simulates grossly as well as microscopically a low-grade squamous cell carcinoma. KAs occur habitually on the mucous membrane as well, but their origin in these cases is debatable, owing to the lack of hair follicles in these sites. Our report is an attempt to demonstrate the cells that could be responsible for initiation of this lesion on the oral mucosa.