Focal nodular hyperplasia of the liver. An electron microscopic study of the vascular lesions.

Localized myointimal proliferation with narrowing of blood vessels is frequently seen associated with focal nodular hyperplasia of the liver. The apparent increase in the incidence of focal nodular hyperplasia in women may be associated with the oral use of contraceptive medications, and it has been suggested that the nodules could be areas of focal cirrhosis following liver infarction. A light and electron microscopic study was undertaken to try to determine the pathogenesis of the vascular abnormalities. The observation of intravascular coagulation, recurrent endothelial damage, and myointimal proliferation about bifurcations suggests that the changes could be produced by repeated platelet-fibrin aggregate embolic injury.