ABSTRACT: Hepatocellular adenomas (HCA) are rare benign tumors mainly developed in women after 2 years of oral contraceptive use (Rooks et al., 1979). HCA are also related to other risk factors (obesity, vascular diseases, androgen and alcohol intake) or to different genetic diseases (Mac Cune Albright syndrome, glycogen storage diseases type 1a and MODY3 diabetes caused by HNF1A germline mutation) (Calderaro et al., 2013; Nault et al., 2013a). Bleeding and malignant transformation to hepatocellular carcinoma (HCC) can occur as severe complications observed respectively in 30-50% and 5% of the cases. In the past 10 years, we identified 4 major molecular subgroups of HCA defined by (1) mutations inactivating HNF1A (H-HCA, 35% of the HCA) (Bacq et al., 2003; Bluteau et al., 2002; Jeannot et al., 2010), (2) activation of ß-catenin by mutations in exon 3 (bHCA, 15%) (Chen et al., 2002), (3) inflammatory phenotype with STAT3 activation (IHCA, 50%) (Bioulac-Sage et al., 2009; Zucman-Rossi et al., 2006), (4) a tumor subgroup of HCA with Sonic Hedgehog pathway activation due to recurrent focal deletions (shHCA) (Nault et al. ,in preparation) and (5) the remaining unclassified tumors (UHCA, 10%) (Bioulac-Sage et al., 2009). Among bHCA, half displayed both inflammatory and ß-catenin activated phenotypes (bIHCA). Inflammatory adenomas (IHCA) are caused by IL6ST somatic mutation activating gp130 in 60% of the cases (Rebouissou et al., 2009) whereas other IHCA are mutated for STAT3 itself (Pilati et al., 2011) or GNAS (Nault et al., 2012) but in the remaining 30% cases no mutation (NM) were identified yet. This molecular classification is currently accepted in clinical practice using either immunohistochemical markers (Bioulac-Sage et al., 2009; Bioulac-Sage et al., 2007) or in radiology at MRI (Laumonier et al., 2008) and it has dramatically improved the diagnosis and prognostic assessment of HCA. HCC derived from HCA malignant transformation (HCC on HCA, 5%)
