Hepatocellular carcinoma presenting well differentiated, normotrabecular patterns in peripheral or metastatic loci. Analysis of 103 resected cases.

In a series of 103 surgically resected hepatocellular carcinomas (HCCs), the tumor boundaries were rather clearly defined in 85 cases (82.5%). Twelve tumors had an ill-defined margin because adjacent pseudolobules were replaced by HCC with a well differentiated growth pattern (group A1). This peripheral pattern was unrelated to the predominant histologic type of the major tumor nodules. Despite its close resemblance to normal hepatic parenchyma, we were able to determine the area of the normotrabecular HCC on the basis of, differences in stain-ability, variable nuclear crowding and frequent microacinar formation. Moreover, scattered occurrence of nuclear atypia and midtrabecular conversion were also observed within the normotrabecular HCC. In an additional 6 cases, a band-like zone of normotrabecular HCC was evident peripherally around the primary lesion (group A2). Fourteen other cases (13.6%) had intrahepatic metastatic lesions formed either within the portal vein or in pseudolobules. Of these, 5 cases showed intrapseudolobular metastases with a normotrabecular pattern (group B). For precise evaluation of surgical HCC specimens, it seems to be particularly important to realize that HCCs sometimes have a highly differentiated appearance in a locus of peripheral invasion as well as intrahepatic metastasis.