A 62-year-old patient complains of a painless formation on his tongue that appeared several months ago. Objectively: the patient has a lot of carious and completely decayed teeth, lateral surface of tongue exhibits a painless whitish formation 10x5 mm large with irregular surface in form of verrucae. Histological examination revealed thickening of corneal epithelial layer of intermittent keratinization type. What is the most likely diagnosis?