Review ArticlesThe Use of Cytokeratin 19 (CK19) Immunohistochemistry in Lesions of the Pancreas, Gastrointestinal Tract, and LiverJain, Richa MBBS, MD; Fischer, Sandra MD; Serra, Stefano MD; Chetty, Runjan MB BCh, FRCPath, DPhilAuthor Information Department of Pathology, The Toronto General Hospital, University Health Network/University of Toronto, Toronto, Canada Reprints: Runjan Chetty, MB BCh, FRCPath, Dphil, Department of Pathology, The Toronto General Hospital, University Health Network/University of Toronto, 200 Elizabeth Street, 11th Floor, Eaton Wing, Toronto, Ontario M5G 2C4, Canada (e-mail: [email protected]). Received for publication March 3, 2009 accepted May 6, 2009 Applied Immunohistochemistry & Molecular Morphology: January 2010 - Volume 18 - Issue 1 - p 9-15 doi: 10.1097/PAI.0b013e3181ad36ea Buy Metrics Abstract Cytokeratin immunostaining forms the bedrock of the immunohistochemical evaluation of tumors. Cytokeratin 19 (CK19) belongs to a family of keratins, which are normally expressed in the lining of the gastroenteropancreatic and hepatobiliary tracts. CK19 immunohistochemistry has been used successfully in thyroid tumors to recognize papillary carcinomas for some time. However, its use in the pancreas, liver, and gastrointestinal tract (GIT) has only recently come to the fore. The purpose of this review is to look at the use of CK19 immunohistochemistry in tumors occurring at these sites. CK19 has been shown to be an independent prognostic factor for pancreatic neuroendocrine tumors, especially the insulin-negative tumors. CK19 positive tumors are associated with poor outcome irrespective of the established pathologic parameters such as size, mitoses, lymphovascular invasion, and necrosis. It is recommended that CK19 be part of the immunohistochemical panel in the work-up of pancreatic endocrine tumors. CK19 is positive in the most of neuroendocrine tumors occurring in the rest of the GIT, except rectal tumors, which are negative. In the liver, CK19 is of prognostic value in hepatocellular carcinomas and is of use in distinguishing cholangiocarcinoma from hepatocellular carcinomas. It can also be used to highlight native ductules in the liver and helps separate conditions such as focal nodular hyperplasia from hepatic adenoma. The vast majority of adenocarcinomas in the GIT and pancreas are CK19 positive. © 2010 Lippincott Williams & Wilkins, Inc.