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
Internal malignancy
External malignancy
Both 1 & 2
None of the above