Focal Nodular Hyperplasia : Microscopic
The hepatocytes of focal nodular hyperplasia (FNH) resemble normal liver parenchyma and are arranged in thin plates (no more than 2 cells thick). The usual cord arrangement in relation to sinusoids, central veins, and the portal tracts is missing. The hepatocytes may show variable cytoplasmic glycogenation. Large, thick-walled vessels surrounded by connective tissue favor FNH over liver cell adenoma, which has thin-walled vessels and scant perivascular connective tissue stroma. The fibrovascular stroma in FNH often contains a lymphocytic infiltrate with occasional neutrophils, eosinophils, plasma cells or histiocytes. The inflammatory cells are more common around bile ductular structures. Granulomas are rare.