Update on the New Classification of Hepatic Adenomas Clinical, Molecular, and Pathologic Characteristics

Context.-Hepatic adenoma is an uncommon, benign, hepatic neoplasm that typically occurs in women of childbearing age, often with a history of long-term use of oral contraceptive drugs. This is usually detected as an incidental mass lesion in a noncirrhotic liver during imaging studies. Pathologic evaluation by needle core biopsy remains the gold standard for diagnosis. Molecular studies have revealed that hepatic adenomas involve unique molecular pathways that are distinct from hepatocellular carcinoma. Based on these studies, a French collaborative group has recently proposed a molecular-pathologic classification for hepatic adenomas. In addition, advances in molecular studies have led to reclassification of the "telangiectatic variant of focal nodular hyperplasia'' as "hepatic adenoma, inflammatory subtype.'' Objective.-To review the proposed, new classification of hepatic adenoma and the changes in diagnostic workup in light of the above-mentioned developments. Data sources.-Review of published literature and illustrations from clinical case material. Conclusions.-Definitive diagnosis of liver mass lesion on needle core biopsies has a decisive role in clinical management. With the advent of the new classification of hepatic adenomas and its prognostic implications, it is vital for pathologists to be aware of the morphologic features seen in different subtypes and the available diagnostic tools, such as immunohistochemistry, to help identify the correct subtype.