Hepatic adenoma.Biochemical and electron microscopic study

Five cases of benign tumors of the liver designated as hepatic adenomas were examined. In addition to light microscopy, tissues were available from 2 cases for electron and biochemical analyses. The gross appearance of these tumors was characterized by the central fibrous tissue core, with peripheral extensions producing nodulation. Light and electron microscopy revealed that these tumors were composed of normal-appearing hepatic cells and bile ducts, lacking only the organization into hepatic lobules. Another characteristic feature was the proliferation of bile ducts in the centers of the tumor nodules. The most striking finding was the excessive accumulation of cytoplasmic glycogen in some of these tumors. However, biochemical analysis demonstrated normal values of the enzymes which are deficient in glycogen storage diseases. In addition, the activity of those enzymes decreased in experimental hepatomas was within normal limits in our material, thus indicating the benign nature of these lesions. Differentiation of regenerative hyperplasia, hamartoma, and adenoma of the liver is discussed.