Malignant form of intraoral acanthosis nigricans is associated with:

Acanthosis nigricans is an acquired dermatologic problem characterized by the development of a velvety, brownish alteration of the skin. In some instances, this unusual condition develops in conjunction with a malignancy, usually gastrointestinal cancer, and is termed malignant acanthosis nigricans. The cutaneous lesion itself is benign, yet it is significant because it represents a cutaneous marker for internal malignancy. Ref: Neville's  oral and maxillofacial pathology 4th edition page 748