Histochemical and immunohistochemical analyses of primary carcinoma of the liver.

Hematoxylin and eosin (H-E) stained liver sections of 47 autopsy cases of hepatic malignancies were examined. There were 43 cases of hepatocellular carcinoma (subtypes of 30 trabecular, 7 solid, 5 pseudoglandular, and one scirrhous carcinoma), 3 of cholangiocellular carcinoma and one of mixed carcinoma. After immunohistochemical staining, benign hepatocytes reacted positively with anti-epithelial membrane antigen (EMA). Hepatocellular carcinoma cells reacted more weakly than benign hepatocytes. It was noted that the microtubular structure, which could not be demonstrated even by alcian blue or cationic ferric hydroxide colloid stabilized with cacodylate (Fe-CaC), was clearly detected with anti-EMA. The EMA-positive microtubular structures may indicate terminal cholangiolar differentiation. Based on EMA, seven more cases formerly classified as hepatocellular carcinoma by H-E were reclassified as mixed carcinoma, totaling eight (17.0%). The histologic classification of "mixed carcinoma" has been 1.5 to 2.0% of primary liver cancers in Japan, but we suggest there may be more cases of "mixed carcinoma" identified in the future. In conclusion, we emphasize that EMA staining is useful for more accurate classification of hepatic tumors.