Cytokeratin 18 (KRT18, CK18) is a Type I intermediate filament chain keratin that is expressed in simple non-stratified epithelial tissues, eccrine glands, trophoblasts and endothelia of veins and lymphatics. Along with KRT8, KRT18 protects the liver from stress-induced injury and apoptosis. Mutations in this gene have been linked to cryptogenic cirrhosis and a variety of liver diseases, particularly after alcohol or viral infections. It is also a serum marker for breast carcinoma and late stage bladder carcinoma. It is positive in a variety of adenocarcinomas and hepatocellular carcinoma, and is generally negative in squamous cell carcinomas. References: Gastroenterol 2005 129(3):885; Hepatology 2007 46(5):1639; Am J Clin Path 123(1):66; Clin Biochem 35(4):327; Histopath 1993 23(1):45