CK8/18

CK8/18 refers to the keratin pair Cytokeratin 8 and Cytokeratin 18, which function together as a major intermediate filament system in simple and glandular epithelium. CK18 has a molecular weight of 45 kDa and naturally pairs with CK8 to form the cytoskeletal network that supports cell structure. This keratin pair is expressed in many normal simple epithelial tissues and in a wide range of adenocarcinomas and other epithelial tumours, while absent in most keratinising squamous carcinomas. Pathologists use CK8/18 as a general marker of simple epithelial differentiation, and CK18 can also serve as a serum tumour marker and a marker of apoptosis in certain contexts (1-2).

Recommended Controls

Criteria for acceptable staining is a membranous and cytoplasmic staining pattern. The recommended controls to include a normal liver, tonsil and a hepatocellular carcinoma. Normal liver, the vast majority of hepatocytes show a distinct, moderate staining reaction with membrane enhancement, while the columnar epithelial cells of the bile ducts show a strong cytoplasmic staining reaction. While the hepatocellular carcinoma should be strongly positive in the tumour cells. Tonsil will be negative.

Expected staining pattern

Hepatocellular carcinoma

Normal liver

Disclaimer

These methods are intended as a guide only. Laboratories that wish to implement these methods should perform internal validation/verification prior to use. The RCPAQAP does not make any claim or warranty for the accuracy or performance of these methods.