Atlas of Diagnostic Pathology (8) : Hepatobiliary System 1: Early Hepatocellular Carcinoma and Hepatocellular Nodules

Early hepatocellular carcinoma (HCC) was designated according to the General Rules for the Clinical and Pathological Study of Primary Liver Cancer, fourth edition, in 2000. Macroscopically, early HCC shows a small indistinct margin nodule. The majority of early HCC cells are uniform in their distribution in well differentiated cancerous tissue with thin trabecular patterns. Tumor cell invasion into the portal tracts retained within the tumor is observed and is defined as stromal invasion. No tumor thrombus in the portal or hepatic veins and no intrahepatic metastasis are seen in early HCC. The other macroscopic types of HCC are considered advanced HCC in spite of their small size because cancer cells show tumor thrombus in the portal or hepatic vein and invasion to the capsule. Hepatocellular nodules with small indistinct margins were classified into regenerative lesions and dysplastic lesions according to the International Working Party in 1995. Dysplastic nodules are regarded as premalignant lesions, but it is often difficult to differentiate early HCC from a dysplastic nodule. We describe the histopathological characteristics of early HCC, advanced HCC, and hepatocellular nodules