Cytokeratin 5 antibody rabbit is a type II intermediate filament protein that is expressed in active basal layers of most stratified squamous epithelia. CK5 is expressed in many non-keratinizing stratified squamous epithelia as well as basal cells in prostate glands and myoepithelial cells in mammary glands. In a published study, rabbit monoclonal CK5 antibody was compared to mouse monoclonal CK5/6. CK5 was 84% sensitive and 100% specific for lung SqCC when compared to CK5/6 (80% sensitivity and 97% specificity). The CK5 predilute has been optimized for lung squamous cell carcinoma; other tumors have not been tested.