Oral acanthosis nigricans: report of a case and comparison of oral and cutaneous pathology.

Malignant acanthosis nigricans is usually associated with adenocarcinomas of the digestive tract. The lesions of acanthosis nigricans commonly run a parallel course to the associated malignancy, producing hyperpigmented, roughened plaques on the skin and, sometimes, verruca-like papules on the oral mucosa. The clinical differences between cutaneous and oral acanthosis nigricans are mirrored by the marked differences in the histopathology. Because oral acanthosis nigricans is uncommon, recognizing histologic features may be difficult. The oral lesions have a true acanthosis and epithelial papillary hyperplasia while the cutaneous forms show slight irregular acanthosis that alternates with areas of epidermal atrophy and dermal papillomatosis.