Specifically, we studied cytokeratin 13 (CK13), found consistently in the suprabasal layers of normal squamous epithelia of the oral cavity with decreased/absent expression in squamous cell dysplasia/carcinoma 29–31, and cytokeratin 6 (CK6), not normally expressed above the basal layer of normal squamous epithelium, but rapidly induced in suprabasal (post-mitotic) cells during conditions of hyperproliferation 32. This evidence concerns the gene KRT13 and carcinoma.