This is the report of an 80-year-old patient with diffuse brownish hyperpigmentation and velvety thickening of the skin with onset 1 year before. Warty lesions on his limbs were present as well as papillomatous and verrucous lesions on his lips, mouth and eyelid conjunctivae with hyperkeratosis of the nipples. Biopsies, performed at different sites, showed histological pictures consistent with a diagnosis of acanthosis nigricans (AN) with florid cutaneous and mucosal papillomatosis. This type of AN is frequently associated with internal malignancy. In our patient serum levels of tissue polypeptide antigen, carcinoembryonic antigen, cytokeratin fragment and squamous cell carcinoma antigen were high and chest computed tomography scan indicated a large tumour infiltrating the right lung and extending to the mediastinum. Cytological examination of bronchial drainage revealed the presence of neoplastic cells, non-small cell type carcinoma. The most frequent cancer associated with malignant AN is gastric adenocarcinoma. Lung tumour has rarely been reported with AN. Malignant AN is sometimes associated with other cutaneous and mucosal warty lesions, as in our patient. These various skin and mucosal lesions are the expression of a systemic epithelial disorder and may help clinicians to suspect a malignant form of AN.