Cytokeratins are proteins of keratin-containing intermediate filaments found in the intracytoplasmic cytoskeleton of epithelial tissue. Cytokeratin represents an excellent marker for the discrimination of specific subtypes of adenocarcinoma. 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.