CK8 is one of the earliest keratins expressed in embryos. It belongs to low-molecular-weight keratins and persists in adult tissues. CK8 is the same as CK18. It is the main component of all simple epithelium, but not expressed in stratified squamous epithelium.
It can mark a variety of normal and tumor glandular epithelium
It is expressed in adenocarcinoma and most cases of non-keratinizing squamous cell carcinoma, but not expressed in keratinizing squamous cell carcinoma.