Focal acantholytic dyskeratosis and epidermolytic hyperkeratosis of the oral mucosa adjacent to squamous cell carcinoma.

A 74-year-old woman presented with an ulcerating squamous cell carcinoma of the posterior mandibular gingiva. Biopsy of the mucosa directly anterior to the tumor revealed areas of both focal acantholytic dyskeratosis (FAD) and epidermolytic hyperkeratosis (EH). Rare solitary lesions of FAD have been described in the oral mucosa; this is the first report of FAD as an incidental finding. EH has only recently been reported in the mouth, and the concept is unknown in the oral pathology literature. Both FAD and EH may represent nonspecific reaction patterns of skin and oral mucosa to numerous stimuli, including carcinogens or adjacent neoplasms.