Mouse Monoclonal, RTU. Intended for in vitro diagnostic (IVD) use. Cytokeratin 20 (CK20) is an intermediate filament protein that reacts with gastric and intestinal epithelium, urothelium, and Merkel cells. It is useful in the identification of specific types of these epithelial cells under normal hyperplastic and neoplastic conditions. CK20 has been detected in adenocarcinomas of the colon, stomach, and biliary tract. Merkel cell carcinomas have shown reactivity. Carcinomas of the breast are generally non-reactive. References 1. Moll R, et al. Identification of protein IT of the intestinal cytoskeleton as a novel type 1 cytokeratin with unusual properties and expression patterns. J Cell Biol. 1990; 111:567-80 2. Moll R, et al. The catalog of human cytokeratins: patterns of expression in normal epithelia, tumors and cultured cells. Cell. 1982; 31:11-24. 3. Han AC, Duszak R Jr. Coexpression of cytokeratins 7 and 20 confirms urothelial carcinoma presenting as an intrarenal tumor. Cancer. 1999; 86:2327-30 4. Moll R, et al. Cytokeratin 20 in human carcinomas: a new histodiagnostic marker detected by monoclonal antibodies. AJP. 1992; 140:427-47. 5. Tot T. Adenocarcinomas metastatic to the liver: the value of cytokeratins 20 and 7 in search for unknown primary tumors. Cancer 1999; 85:171-7. 6. Lau SK, et al. Comparative immunohistochemical profile of hepatocellular carcinoma, cholangiocarcinoma, and metastatic adenocarcinoma. Hum Pathol. 2002; 33:1175-81 7. Rullier A et al. Cytokeratin 7 and 20 expression in cholangiocarcinomas varies along the biliary tract but still differs from that in colorectal carcinoma metastasis. Am J Surg Pathol. 2000; 24:870-6