Scanning electron microscopy of rat liver hyperplastic nodules induced by diethylnitrosamine.

Rat liver hyperplastic nodules induced by diethylnitrosamine (DEN) were observed by scanning electron microscopy (SEM). Liver hyperplastic nodules were made according to the methods of Solt and Farber. Hyperplastic nodules appeared 4 weeks after DEN administration and these early hyperplastic nodules continued growing and became eosinophilic hyperplastic nodules 5 to 6 weeks after DEN administration. SEM revealed that hyperplastic nodules were composed of enlarged hepatocytes which formed two-cell-thick plates. Intercellular surfaces of hepatocytes were covered with numerous microvilli. Dilation of bile canaliculi was marked in hyperplastic nodules. Kupffer cells were not seen in the sinusoids. Sinusoidal endothelia had no fenestrae. Transmission electron microscopy revealed the endothelium had a continuous basement membrane. In conclusion, hyperplastic nodule has the intermediate features between liver cirrhotic nodule and liver cell adenoma or hepatocellular carcinoma.