Intrahepatic metastasis of hepatocellular carcinoma: a histopathologic study.

Developmental processes of intrahepatic metastasis were examined in 75 selected cases of hepatocellular carcinoma (HCC) arising in cirrhotic livers. According to their prevalent sites of formation, metastatic nodules were divided into the portal type (59 of 75, 78.7%) and the acinar type (16 of 75, 21.3%). In general the tumor histology was similar to that of primary lesions. The acinar type usually developed via coalescence of scattered tumor cell clusters formed within pseudolobules. In seven cases classified as acinar type, the nodules were composed of well-differentiated tumor cells which were arranged in trabeculae of almost normal thickness (normotrabecular subtype). In four out of these seven cases, the lesions could be clearly defined as metastatic. The subtype could not be determined when only a few discrete nodules were present, as in the remaining three cases. The nodules of the normotrabecular subtype tended to contain a central core of less-differentiated HCC in association with tumor growth, giving rise to a feature of nodule-in-nodule lesions. It is concluded that there do occur metastatic nodules showing well-differentiated, normotrabecular pattern and that these nodules are available for studying developmental steps of early HCCs.