Focal nodular hyperplasia of the liver: ultrastructural observations.

Ultrastructural studies of the liver from a non-alcoholic 21 year old male with focal nodular hyperplasia (FNH) showed hepatocyte cytoplasmic alterations including swollen and bizarre mitochondria, rough endoplasmic reticulum (RER) in short parallel stacks or whorl-like arrangements, and Mallory bodies (MB). Proliferated bile duct cells contained occasional MB-like inclusions. Small hepatic blood vessels were dilated and some showed interruption and partial loss of their endothelial cell cytoplasm and thickened basement membranes. Liver tissue outside of the lesion appeared unaltered.