Focal nodular hyperplasia or focal nodular hyperplasia-like lesions of the liver: a special emphasis on diagnosis

Background and Aim: Focal nodular hyperplasia (FNH) and FNH‐like lesions are hypervascular masses that can mimic hepatocellular carcinoma (HCC). We have investigated the clinical, radiological and pathological features of FNH and FNH‐like lesions of the liver, with particular focus on the aspect of diagnosis. Methods: A total of 84 patients, 77 with pathologically‐proven FNH and seven with FNH‐like lesions of the liver, were analyzed retrospectively. Results: Of the 84 patients, seven had underlying liver cirrhosis, including two with Budd‐Chiari syndrome and one with cardiac cirrhosis. These cases were therefore classified as having FNH‐like lesions. Two of the remaining 77 patients without underlying liver cirrhosis were positive for hepatitis B surface antigen. Seven of 50 (14.0%) patients evaluated by four‐phase computed tomography (CT) showed portal or delayed washout, and three of 28 (10.7%) patients analyzed by three‐phase CT showed washout on the portal phase. Collectively, three of nine (33.3%) patients with risk factors for HCC could have been wrongly diagnosed with HCC based on the non‐invasive diagnostic criteria for HCC. A central scar was observed in 30 patients (35.7%) radiologically. Among 62 patients who underwent percutaneous needle biopsy, four patients (6.5%) were misdiagnosed as having HCC and two patients (3.2%) had inconclusive results by a first needle biopsy. Conclusions: The presence of a hepatic lesion with arterial hypervascularity and/or portal/delayed washout is not necessarily diagnostic of HCC, particularly in patients without risk factors for HCC. These radiological findings can also occur in cirrhotic patients with FNH‐like lesions, including those with hepatic outflow obstruction.