Cavernous structures composed of hepatocytes in experimentally induced hepatocellular carcinoma.

Cavernous structures composed of hepatocytes were observed for the first time in trabecular-patterned hepatocellular carcinomas by light, scanning and transmission electron microscopy. The carcinomas were induced by a single dose of diethylnitrosamine combined with subsequent administrations of 2-acetylaminofluorene and partial hepatectomy. The cavernous structures had numerous cavities walled by flat hepatocytes. In the cavities, dendritic hepatocytes, connected with each other by their long and slender processes, formed a network and were attached to the fenestrated sinusoidal endothelium via intercellular spaces between the flat hepatocytes. Dendritic hepatocytes had smooth surfaces, prominent nucleoli, decreased glycogen, and well organized cisternae. Dilated bile canaliculi were sometimes seen among flat and dendritic cells. Dendritic cells showed more morphological dearrangement than flat cells. Blood cells were observed in the cavities. Kupffer cells were not seen in the sinusoids among the cavernous structures. The cavernous structures in the hepatocellular carcinomas resembled the hepatocyte arrangement in fetal liver in which intercellular spaces of hepatocytes are extremely widened.