Immunohistochemical pitfalls and the importance of glypican 3 and arginase in the diagnosis of scirrhous hepatocellular carcinoma.

Scirrhous hepatocellular carcinoma is a rare ill-defined morphological subtype of hepatocellular carcinoma characterized by marked stromal fibrosis. This variant can be difficult to distinguish from intrahepatic cholangiocarcinoma and metastatic adenocarcinoma, especially on needle biopsies. We performed immunohistochemistry for hepatocellular and adenocarcinoma-associated markers on 20 scirrhous hepatocellular carcinoma cases and compared the results with classical hepatocellular carcinoma and intrahepatic cholangiocarcinoma. Scirrhous hepatocellular carcinomas were significantly less likely to be HepPar-1 positive than classical hepatocellular carcinomas (26% and 74%, respectively; P<0.001) and were significantly more likely to express adenocarcinoma-associated markers such as epithelial cell adhesion molecule (63 vs 11%; P<0.001), cytokeratin 19 (26 vs 2%; P<0.001), and cytokeratin 7 (53 vs 2%; P<0.001). At least one of these adenocarcinoma-related markers was positive in 80% of scirrhous hepatocellular carcinoma cases. Glypican 3 and arginase were positive in 79% and 85% of cases of scirrhous hepatocellular carcinoma, respectively; the combined use of these two markers yielded 100% sensitivity for scirrhous hepatocellular carcinoma. In conclusion, the scirrhous morphology, absence of HepPar-1 staining, and frequent positivity with adenocarcinoma-related markers in scirrhous hepatocellular carcinoma can lead to an erroneous diagnosis of adenocarcinoma. Glypican 3 and arginase are the most reliable markers for identifying hepatocellular differentiation in this setting.