Hepatocellular adenoma is the most important benign tumor of the liver. Occurring primarily in reproductive females, it has increased in prevalence because of widespread use of [[oral contraceptive]s, which play a role in pathogenesis. Most adenomas are asymptomatic, but adenomas rarely present as an acute surgical problem caused by abrupt rupture and bleeding into the peritoneal cavity. Although adenomas generally are not precancerous, a few cases of malignant transformation have been described. Adenomas related to contraceptive use often regress if the drug is stopped.
On gross pathologic examination, the tumours are large soft yellow to tan masses, often with areas of hemorrhage or necrosis. Microscopically, it is a highly vascular tumour composed of benign hepatocytes.