Oral manifestations as a hallmark of malignant acanthosis nigricans.

We present a case of malignant acanthosis nigricans (AN) that initially manifested in the oral cavity. In the present report, the patient had typical clinical and histological findings of oral and esophageal AN, with subtle skin changes, associated with a gallbladder adenocarcinoma. The importance of the clinical oral examination is emphasized because the recognition of oral lesions led to the diagnosis of AN and to the following detection of the internal malignancy. Since the tumours associated with AN are highly malignant, it is of the utmost importance to recognize the skin and mucous membrane changes in adults.