Ultrastructural study of hepatocellular carcinoma with replacing growth pattern.

The replacing growth of hepatocellular carcinoma (HCC) has been considered as a basic growth pattern at the tumor-nontumor boundary. In order to clarify the ultrastructural characteristics of HCC with the replacing growth, we have studied 59 surgical cases of HCC. At the tumor-nontumor boundary of HCC with the replacing growth pattern, the tumor cells grow to replace the hepatocytes along the liver cell cord, but oppress and distort the adjacent liver cell cord with varying degrees of aggregation of reticulin fiber. Hepatocytes and cancer cells are in direct contact, but some of the hepatocytes are compressed by cancer cells. The sinusoid in the non-cancerous area is continuous with the blood space in the cancerous tissue, and several layers of endothelial cells are often observed. Accordingly, it is predicted that sinusoidal blood through the portal vein and arterial blood through arterial tumor vessels may mix at the tumor-nontumor boundary.