In adults, genomic and molecular studies together with the analysis of genotype/phenotype correlations have led to the recognition of four major HCA subgroups: HNF1-α-inactivated HCA, β-catenin-activated HCA, and two forms of HCA without mutation of HNF1-α or β-catenin presenting either with or without inflammation. This evidence concerns the gene HNF1A and hepatocellular adenoma.