A case of β-catenin-activated hepatocellular adenoma with tert promoter mutation in a young woman not taking oral contraceptives

The patient was a 37-year-old woman not taking oral contraceptives. An 80-mm single nodule was found in S7 of the liver by screening ultrasonography. MRI revealed hypo-intensity on T1WI and iso-intensity on T2WI. CT during hepatic arteriography was strongly enhanced and that during portography demonstrated the nodule to be a defective lesion. The patient underwent percutaneous biopsy. Histopathologically, the biopsied specimens of the inner and outer nodules consisted of hepatocytes with mild atypia. Immunohistochemically, the tumor cells of both regions were positive for β-catenin, suggesting the presence of β-catenin-activated hepatocellular adenoma (b-HCA). The tumor was resected. It exhibited a nodule-in-nodule structure, was 9.8 cm in diameter, and was diagnosed as b-HCA. Mutation analysis revealed a mutation in the telomerase reversetranscriptase (TERT) promoter region only in the inner nodule. The nodule-in-nodule structure and localized TERT promoter mutation of the inner nodule suggested a precancerous change in multistep carcinogenesis.