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Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 18 December 2011, last major update December 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.


● Claudins are large family of tight junction proteins with 4 transmembrane domains
● Claudins function to produce a seal between cells, with critical role in maintaining cell polarity
● Claudin18, first described in 2001 (Mol Cell Biol 2001;21:7380) is highly conserved member, specific for gastric and lung tissue (Gene 2011;481:83)


● Also called CLDN18

Clinical features

● Expression may contribute to greater acid resistance of Barrett's esophagus (Am J Physiol Gastrointest Liver Physiol 2007;293:G1106)


● Membranous staining

Micro images

Normal lung and stomach (Claudin18 Splice Variant 2)

Pancreas: PanIN (left), infiltrating ductal carcinoma (right)

Carcinomas of stomach, esophagus, ovary (Claudin18 Splice Variant 2)

Positive staining - disease

Bile duct: biliary intraepithelial neoplasia (78%), extrahepatic bile duct carcinoma (90%), intrahepatic (100%) and extrahepatic (89%) intraductal papillary neoplasm of bile duct (100%), intrahepatic cholangiocarcinoma (43%, Virchows Arch 2011;459:73)
Pancreas: PanIN, intraductal papillary mucinous neoplasms, mucinous cystic neoplasms, infiltrating ductal adenocarcinoma (Am J Surg Pathol 2008;32:188, J Histochem Cytochem 2011;59:942)
● Signet ring adenocarcinoma (gastric 86%, colorectal 38%, not breast or lung, Am J Surg Pathol 2008;32:1182)
● Urachal adenocarcinoma (Am J Surg Pathol 2011;35:787)

Negative staining - disease

● Non-neoplastic pancreas
● Urachal remnants and benign disorders (Am J Surg Pathol 2011;35:787)

End of Stains > Claudin18

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