Cytokeratin 17 is a 46 kD intermediate filament that is present in simple epithelia and serves as a marker for cervical reserve (stem) cells. CK17 can be used to identify uterine cervical squamous lesions, such as atypical immature metaplasia, cervical intraepithelial neoplasia, and cervical squamous carcinoma. Additionally, CK17 helps distinguish between different types of oral squamous cell carcinoma.