Histologic diagnosis of hepatic tumors.

Many types of tumors, benign and malignant, primary and metastatic, can occur in the liver. Diagnostic criteria for two relatively common and two uncommon primary malignant liver tumors are presented. Hepatocellular carcinoma, the most common primary malignant hepatic tumor, is recognized when the tumor cells show features of liver cell differentiation, such as a trabecular growth pattern, intercellular bile canaliculi, eosinophilic granular cytoplasm, bile production or other hepatic synthetic products. Intrahepatic cholangiocarcinoma shows glandular differentiation, similar to other adenocarcinomas. It often cannot be distinguished from metastatic adenocarcinoma, and the diagnosis requires the exclusion of an extrahepatic primary site. Undifferentiated (embryonal) sarcoma is a rare primary liver tumor of children and young adults. It shows undifferentiated stellate and spindle cells in a myxoid matrix. Hepatic angiosarcoma is a malignant endothelial cell proliferation, beginning in the hepatic sinusoids, eventually filling the vascular structures, and often progressing to tumorous vascular masses. The histologic diagnosis of all types of liver tumors requires the application of strict morphologic criteria to light microscopic observations. Diagnoses that do not conform to such criteria are often inaccurate.