Hepatocellular Adenomas: Morphology and Genomics.

Hepatocellular adenomas (HCAs) are rare benign tumors. This single entity has been split into 3 subtypes corresponding to specific mutations: HNF1α-inactivated HCA; inflammatory HCA related to different mutations, all leading to activation of STAT3 pathway; and β-catenin-activated HCA related to CTNNB1 mutations. The risk of malignant transformation depends on the level of β-catenin activation, reported mainly for exon 3, including S45. It is possible using specific immunohistochemical markers to identify the 3 different HCA subtypes and the level of β-catenin activation. Fewer than 10% of HCAs remain unclassified.