Acanthosis nigricans (AN) is a rare condition which may affect oral cavity. There are two forms of AN: benign and malignant. Benign AN may be hereditary, or may be related to systemic diseases or drugs. Malignant AN is most often associated with gastric adenocarcinoma but cancers of other sites and types may also occur. This case report is based on a case of a 78-year-old woman suffering from invasive bladder papillary transitional cell carcinoma accompanied by extensive papillomatous areas of normal mucosal color and soft consistency involving the lips, buccal mucosa and hard palate. Verrucous changes with tiny pigmented macules were also found on the skin of the right ear auricle. Oral lesions occurred after the tumor had been diagnosed, i.e. after third operation for tumor recurrence. The fifth operation for tumor recurrence resulted in slight improvement of oral changes. It is concluded that the severity of oral changes is in correlation with tumor progression. The occurrence of oral lesions may be an indicator of tumor progression.