RADIOLOGY: HEPATOBILIARY: Case# 59: FNH. This is a 30 year old black female on birth control pills. The patient had a previous CT which revealed an exophytic cystic appearing lesion within the left lobe lateral segment of the liver. A lesion within the left lobe lateral segment that is somewhat exophytic is present. The cystic portion of this lesion measures 4 x 5 x 5.7 cms. A 2nd hyperdense lesion within the right lobe anterior segment measuring 6 x 6.5 cm is also present, seen only on the portal venous phase. No cystic component is present within this enhancing lesion in the right lobe. No other focal lesions are identified within the liver. A benign hepatic tumor found more commonly in women(2:1-7:1), focal nodular hyperplasia is usually an asymptomatic solitary tumor that is discovered incidentally. Seven percent of patients, however, will have multiple tumors. Focal nodular hyperplasia contains histologically normal liver elements and has no known malignant potential. Hemorrhage, tumor infarct, and rupture are rare complications while fibrous bands and stellate fibrous scars are common. Management of asymptomatic lesions is controversial although elective surgical resection is usually performed. Observation may be warranted if surgery would be hazardous or difficult. The typical imaging of FNH is a hypodense homogeneous mass on unenhanced CT scan and a hyperdense or isodense mass on enhanced CT. FNH may be differentiated from adenoma by the absence of hemorrhage which is nearly always found within adenomas; however, if hemorrhage is not evident, then radionuclide scintography should be performed. Radionuclide uptake in FNH is normal in 40-70% on technetium-99m labelled sulfur colloid liver scan whereas radionuclide uptake is absent within adenomas. In addition, there are multiple tumors in 30% of patients with hepatic adenoma in contrast to 7% in FNH.