Cytokeratins are a subfamily of intermediate filament proteins and are characterized by a remarkable biochemical diversity, represented in Human epithelial tissues by at least 20 different polypeptides. They range in molecular weight between 40 kDa and 68 kDa and isoelectric pH between 4.9 – 7.8. The individual Human Cytokeratins are numbered 1 to 20. The various epithelia in the Human body usually express Cytokeratins which are not only characteristic of the type of epithelium, but also related to the degree of maturation or differentiation within an epithelium. Cytokeratin subtype expression patterns are used in the distinction of different types of epithelial malignancies. The Cytokeratin antibodies are of assistance in the differential diagnosis of tumors using immunohistochemistry on tissue sections.

 

Cytokeratin 17 (CK17) is an intermediate filament protein expressed in the basal cells and myoepithelial cells of complex epithelia, including glandular epithelium with myoepithelial component, transitional and pseudostratified epithelia. CK17 is a marker in the identification of breast cancer with basal phenotype. Squamous cell carcinoma is also labeled by CK17 antibody. Antibody against CK17 may be an aid in distinguishing cholangiocarcinoma (CK17+) from hepatocellular carcinoma (CK17-). In combination with MUC1, CK17 antibody has been found to be useful in distinguishing pancreatobiliary adenocarcinoma (CK17+) from extrapancreatobiliary nonmucinous adenocarcinoma (CK17-).