(A) There is extension of atypical keratinocytes beyond the basement membrane and into the dermis. (H&E stain, ×100, Inset: H&E stain, ×40). (B) At high power magnification, there are irregular masses of epidermal cells that are predominantly mature squamous cells showing relatively slight atypicality. More than 75% of the tumor is keratinized. (H&E stain, ×200).