Immunohistochemistry with different
cytokeratin subsets has been successfully used in the differential diagnosis of various human
epithelial neoplasms.
Cytokeratin 5/6 antibody, which recently became commercially available, has been found useful in the diagnosis of
mesothelioma. Studies have reported only infrequent staining in
adenocarcinomas. We investigated the pattern of immunoreactivity for
cytokeratin 5/6 in hepatobiliary and pancreatic
tumors to determine its diagnostic utility in the morphologic evaluation of these
neoplasms.
Formalin-fixed.
paraffin-embedded tissue sections from 10
hepatocellular carcinomas, seven
hepatocellular adenomas, 10
cholangiocarcinomas, 10 pancreatic ductal
adenocarcinomas, and 13 pancreatic
neuroendocrine carcinomas were immunostained with anticytokeratin 5/6 after heat-induced
antigen retrieval utilizing a modified
avidin-
biotin complex technique. Positive and negative controls stained appropriately. Two pathologists evaluated the slides. Strong but focal cytoplasmic immunoreactivity was observed in five of 10 pancreatic ductal
adenocarcinomas and two of 10
cholangiocarcinomas. No immunoreactivity was identified in any cases of
hepatocellular carcinoma (0/10),
hepatocellular adenoma (0/7), or pancreatic
neuroendocrine carcinoma (0/13). Additionally, occasional
cytokeratin 5/6 immunoreactive benign ductal epithelial cells were seen in the background in some cases. Fifty percent of pancreatic ductal
adenocarcinomas and 20% of
cholangiocarcinomas are positive with anti-
cytokeratin 5/6 immunostaining. For the evaluation of poorly differentiated
neoplasms in the liver, immunoreactivity with
cytokeratin 5/6 may help to exclude the possibility of
hepatocellular carcinoma.
Cytokeratin 5/6 may be helpful as a component in the panel of immunostains to differentiate between poorly differentiated
neoplasms.