背景：Cytokeratin 5 (CK5) is a basic protein closely related to cytokeratin 6. They have similar tissue distribution and present in different proportions in many non-keratinized stratified squamous epithelium, such as tongue mucosa, tracheal basal epithelium, epidermal basal cells, hair follicles, skin sebaceous and sweat glands, breast cavity cells, prostate basal cells, urethra epithelial cells, vagina and cervical endometrium. Cytokeratin 5 and 6 are also expressed in basal cell epithelioma, squamous cell carcinoma of the skin, tongue, epiglottis and anorectal area.
