Focal nodular hyperplasia of the liver: a study of 21 pediatric cases.

Twenty-one cases of focal nodular hyperplasia of the liver in pediatric patients are presented and compared with 40 cases previously reported. In this series, the lesion was usually asymptomatic (95%) and presented as a nontender mass noted on routine physical examination or was discovered incidentally at autopsy. There was a distinct female predominance (81%). Radiographic examination demonstrated a vascular space-occupying hepatic mass. The lesions were noted bilaterally or in the left lobe in 62% of cases. They were large, nonencapsulated, firm masses with central stellate areas subdividing the lesions into multiple lobules. Microscopically, septa contained eccentrically thickened vessels, small bile ducts, and an acute and/or chronic inflammatory infiltrate. Hepatocytes resembled those of the normal liver but some contained increased glycogen and fat. The lesions had no malignant potential and, except in women taking oral contraceptives, could be treated conservatively.