CK 8/18 (Cytokeratin 8/18) is expressed in monolayer epithelium or glandular epithelium of normal or tumor tissues. It is expressed in adenocarcinoma and the vast majority of nonkeratinizing squamous cell carcinoma, while keratinizing squamous cell carcinoma does not. It combined with CK5/6 for diagnosis adenocarcinoma and squamous cell carcinoma.