Successful resection of a huge hepatocellular adenoma.

Hepatocellular adenoma (HCA) is a rare benign liver tumor that has been reported to occur particularly more often in women who use contraceptives. A 72-year-old woman with no history of using contraceptives presented to our hospital for further examination of a liver tumor. Contrast-enhanced computed tomography and gadoxetic acid-enhanced magnetic resonance imaging revealed a huge solitary hepatic tumor measuring 83 × 76 mm in segments 4, 5, and 8. The differential diagnoses were cholangiocarcinoma and mixed-type hepatocellular carcinoma. Percutaneous needle biopsies were performed twice, and no malignant components were found. Central bi-segmentectomy of the liver was successfully performed. Immunohistochemical staining showed that β-catenin was positive in the membrane of the tumor cells, while fatty acid-binding protein, glutamine synthetase, and amyloid A were negative. These results led to a diagnosis of HCA, hepatocyte nuclear factor-1α-inactivated subtype. The patient's postoperative course was uneventful, and she developed no recurrence for 10 months after surgery. We experienced a rare case of benign HCA. Obtaining a correct preoperative diagnosis is sometimes difficult at the first evaluation. HCA should be considered as a differential diagnosis of liver tumors.