A case of focal nodular hyperplasia difficult to diagnose preoperatively

Focal nodular hyperplasia (FNH) may be difficult to differentiate from hepatocellular carcinoma (HCC). We report a case of FNH with unusual MRI and Sonazoid US fingings. A 41-year-old woman with hepatitis B virus and suffering from epigastralgia was found to have serum liver function test and tumor marker results within normal limits. Contrast-enhanced computed tomography (CT) showed a 3cm high-density area with a central nonenhanced lesion having a central scar-like center in segment 1. Sonazoid US showed a 'spoke wheel sign' in the early vascular phase, but a defect in the postvascular phase. Superparamagnetic iron oxide MRI showed decreasing uptake. Due to the possibility of HCC, we conducted a hepatic caudate lobectomy. The pathological examination indicated FNH. Given that Kupffer cells are not reflected in some image findings, it is important to conduct a microscopic diagnosis, including resection, to definitively rule out FNH.