New monoallelic (partial tandem duplication) mutation of HNF1a gene in steatotic hepatocellular adenoma.

Hepatocellular adenomas (HCAs) containing inactivating HNF1a mutations correspond to a homogenous group of tumors with marked steatosis and no cytological abnormalities or inflammatory infiltrates. We report a case of a 60-year-old woman who was referred with a 13-cm mass in the left lobe of the liver with no history of oral contraception use and no family history of note. Histology revealed a severely steatotic HCA. Immunohistochemistry showed no nuclear staining for β-catenin, limited glutamine synthetase positivity, and slightly attenuated liver-fatty acid binding protein staining. Serum amyloid A2 antibodies produced a coarse granular staining. Mutational screening detected monoallelic partial tandem duplication within exon 4 of TCF1 in tumoral tissue. No mutations in the β-catenin and IL6ST genes were detected. Quantitative reverse transcription PCR showed lower expression levels of FABP1 and uridine glycosyltransferase 2B7 and higher levels of serum amyloid A2 in tumor than in normal hepatocytes. Clinicopathological and molecular investigation of HCA cases with unique features could result in a better understanding of HCAs pathogenesis.