Keratins 6 and 16 are expressed in keratinocytes, which are undergoing rapid turnover in the suprabasal region (also known as hyperproliferation related keratins). Keratin 6 is found in hair follicles, neck squamous cell carcinomas, suprabasal cells of a variety of internal stratified epithelia, in epidermis, in both normal and hyperproliferative situations. Epidermal injury results in activation of keratinocytes which express CK6 and CK16. CK6 is strongly expressed in about 75% of head and neck squamous cell carcinomas. Expression of CK6 is particularly associated with differentiation. There are at least six isoforms of human type II keratin 6 (K6), K6A being the most abundant representing about 77% of all forms found in epithelia.