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A 27-year-old man, previously healthy, had an enlarging liver mass incidentally noted at a health check-up 6 months earlier. There were no known risk factors for hepatocellular carcinoma. The hepatic tumour seen on magnetic resonance imaging had characteristics of high T2 and low T1 signals, early hyper-enhancement and mild delayed enhancement, which was atypical for focal nodular hyperplasia (FNH). An atypical hepatectomy was performed smoothly and the pathologic confirmation of FNH was finally made. He was discharged without complications.
Focal nodular hyperplasia (FNH) is a benign liver tumour, but sometimes it can cause diagnostic difficulty in clinical practice. Differential diagnosis in imaging may not be conclusive as our case suggests. Here we demonstrate a case of atypical presentation of FNH, both in the patient’s history and in the imaging findings. Differential diagnosis and management strategy are discussed.
A previously healthy 27-year-old man had an enlarging hepatic tumour incidentally noted at the health check-up 6 months previously, increasing from 2 cm to 2.5 cm in maximal diameter. He had no hepatitis virus B or C infection and denied alcohol consumption. Serum values of liver enzymes were normal and α-fetoprotein (AFP) was 1.91 ng/ml. Follow-up abdominal magnetic resonance imaging (MRI) was performed (fig 1). An atypical hepatectomy was also performed, and the gross pathologic specimen is shown in fig 2. Focal nodular hyperplasia was diagnosed pathologically. The patient was subsequently discharged without any complications.
FNH predominantly occurs in young females and MRI is the diagnostic modality of choice. The typical features at MRI include homogeneously isointense or slightly hyperintense tissue on T2 weighted images, the presence of a central stellate area, pronounced enhancement of the lesion in the arterial phase, accumulation of gadolinium chelates within the central scars on delayed T1 weighted images, and absence of tumour capsule.1 The central scar, which may not be seen in imaging studies, typically consists of fibrous connective tissue, cholangiocellular proliferation with inflammatory infiltrates and malformed vessels, including tortuous arteries, capillaries and veins,2 as shown in fig 2.
FNH is rare in men and the lesions are usually smaller and more often atypical (for example, no central stellate area on MRI, over high/low or heterogeneous signal intensity on T2 weighted images) than those in women (72.2% vs 16.7%),3 which may pose diagnostic difficulty as in our case. Hepatocellular carcinoma can be presented with a central scar in non-cirrhotic patients but usually occurs in their 60s.4 Fibrolamellar carcinoma is a large slow growing tumour which occurs at a young age with low AFP values and a normal liver, and could also present with central scars.5 Resovist enhanced MRI may be helpful to differentiate benign lesions from malignant ones.6
Practically speaking, if the lesion is small and all other tests are negative, a follow-up MRI scan in 3–6 months to assess for growth may be all that is required, particularly if a central scar is seen on MRI that is compatible with FNH.7 The enlarging hepatic tumour together with atypical MRI features in this patient, however, makes malignancy likely, and therefore justifies surgical resection and further pathologic confirmation.
Competing interests: None.
Patient consent: Patient/guardian consent was obtained for publication.