Focal nodular hyperplasia is an uncommon benign lesion of the liver, usually diagnosed in women aged 20–50 years. Although some patients are symptomatic with pain in the right upper quadrant of the abdomen, the majority are asymptomatic and are diagnosed incidentally during upper abdominal imaging. Macroscopically, lesions are light brown or gray with a central stellate scar and radiating fibrous septa. Histologically, the appearance resembles inactive cirrhosis. One possibility is that the lesion develops as a hyperplastic response of the liver to a pre-existing vascular malformation. This could account for associations with hereditary hemorrhagic telangiectasiae and congenital absence of the portal vein. The relationship of focal nodular hyperplasia to use of hormone preparations is still debated but oral contraceptives or other hormone preparations may increase the size of the nodules. The natural history is highly variable and includes stable lesions, progressive lesions and regression with approximate frequencies of 60%, 10% and 30%, respectively. Surgical resection is only required for symptomatic and expanding lesions or if the diagnosis remains in doubt. In the patient illustrated below, relatively large lesions regressed either spontaneously or because of cessation of hormone preparations.

A young woman was referred for evaluation in 1991 with intermittent pain in the right upper quadrant of her abdomen that persisted after a cholecystectomy for gallstones. Retrograde cholangiography was normal. She subsequently had courses of danazol and medroxyprogesterone acetate for endometriosis and infertility. In 2000, a computed tomography (CT) scan was performed because of persisting abdominal discomfort and abnormalities on an ultrasound study that raised the possibility of a large hemangioma. A contrast-enhanced CT scan showed a large lesion, 10 cm in diameter, in segment 4 of the liver and a smaller lesion, 5 cm in diameter, in segment 6. Lesions were shown in both the arterial and portal venous phases and both lesions had central scars. Lesions in the portal venous phase are shown in Figure 1. She was advised to avoid hormone preparations and a repeat ultrasound study in 2001 showed a stable lesion in the left lobe of the liver. A CT scan was repeated in 2010. No definite lesions were seen in the arterial phase but a small residual abnormality was shown in segment 4 in the venous phase (Figure 2). Her upper abdominal symptoms have improved but she continues to have intermittent epigastric discomfort as well as intermittent abdominal distension.

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