An ultrastructural comparison of sinusoids in hepatocellular carcinoma, adenomatous hyperplasia, and fetal liver.

: Transmission and scanning electron microscopic examinations were performed to evaluate the fine-structural differences in sinusoids of hepatocellular carcinoma, adenomatous hyperplasia of the liver, and fetal livers. In cancerous sinusoids, thickened endothelial cells with loss of sieve plates were conspicuous features. In the sinusoids of adenomatous hyperplasia, scanning electron microscopy showed apparent sieve plates, and basement membrane formation (capillarization) was less conspicuous than in carcinoma. In fetal livers, occasional large gaps as well as small fenestrations in the endothelium were noted. Basement membrane materials were not seen. It was concluded that the sinusoids of hepatocellular carcinoma lost the fine-structural nature of normal sinusoids and showed much more prominent capillarizations than the sinusoids of adenomatous hyperplasia, and that the fine structures of cancerous sinusoids were also different from those of the sinusoids in fetal livers.