Intraoral and labial keratoacanthoma.

Keratoacanthoma (KA) is a relatively common skin lesion of questionable histogenic origin. Although cutaneous KAs are considered to arise from hair follicles, the rare cases reported occurring on mucous membranes would suggest possible origin from surface epithelium. A review of the literature revealed six previous cases involving oral mucosa. Seven new cases of keratoacanthoma are presented. Four occurred on the lower lip, and three arose from intraoral mucosal tissue, accounting for a total of nine reported intraoral cases.