The Diagnostic Value of Immunohistochemistry in the Diagnosis of Primary and Secondary Hepatic Carcinomas

Metastatic adenocarcinoma to the liver from an unidentified primary tumor site is a common diagnostic problem. The present study included 41 cases of histologically diagnosed liver biopsies including hepatocellular carcinoma, cholangiocarcinoma and metastatic carcinoma in the liver. All cases were stained immunohistochemically with Cytokeratin 18, 7, and 20, Carbohydrate Antigen 19-9 and Alpha-fetoprotein to evaluate their usefulness in differentiating these tumor entities. Cytokeratin 18 was positive in 87.5% of hepatocellular carcinoma; all cases of cholangiocarcinoma, and metastatic carcinoma. Cytokeratin 7+ve/Cytokeratin 20-ve pattern was identified in 12.5% of hepatocellular carcinoma, 100% of cholangiocarcinoma, one metastatic pancreatic carcinoma, and all metastatic gastric carcinomas (100%). On the other hand, Cytokeratin 7-ve/Cytokeratin 20+ve were identified in colorectal carcinoma metastatic to the liver. CA19-9 showed positive immunoreactivity in all studied cases. AFP positive immunostaining was identified in 43.7% of hepatocellular carcinoma while it was negative in all other tumors. It was concluded that Cytokeratin 18 was of no benefit in the differential diagnosis of primary hepatic carcinoma and metastatic cases from any site. Cytokeratin 7 and CA19-9 positive staining can exclude a diagnosis of hepatocellular carcinoma, but cannot discriminate between metastatic carcinoma (from stomach, pancreaticobiliary origin) and cholangiocarcinoma. The Cytokeratin 20+/Cytokeratin 7-ve phenotype indicates metastatic intestinal adenocarcinoma, most often from the colon or rectum.