Hepatocellular adenoma is a rare, benign liver tumor. It most commonly occurs in people with elevated systemic levels of estrogen, classically in women taking estrogen-containing oral contraceptive medication.
Signs and symptoms
About 25–50% of hepatic adenomas cause pain in the right upper quadrant or epigastricregion of the abdomen. Since hepatic adenomas can be large, patients may notice a palpable mass. However, hepatic adenomas are usually asymptomatic, and may be discovered incidentally on imaging ordered for some unrelated reason. Large hepatic adenomas have a tendency to rupture and bleed massively inside the abdomen. If not treated, there is a 30% risk of bleeding. Bleeding may lead to hypotension, tachycardia, and sweating.
Hepatic adenoma is usually detected by imaging, typically an ultrasound or CT, as a hyperenhancing liver nodule. Given that several liver tumors appear similarly on these imaging modalities, a multi-phase contrast-enhanced imaging study such as CT or MRI may be used to provide more information. The significance of making a specific diagnosis is that, unlike other benign liver tumors such as hemangioma and focal nodular hyperplasia, hepatic adenomas have a small but meaningful risk of progressing into a malignancy. Although imaging provides supportive information, a definitive diagnosis of hepatic adenoma requires biopsy of the tissue.
Hepatic adenomas may be sub-classified according to morphologic appearance by microscopy, immunohistochemical staining, and genetic mutational analysis:
Inflammatory
HNF1α-inactivated
β-catenin–activated - with exon 3 versus exon 7/8 mutation
β-Catenin–activated inflammatory - with exon 3 versus exon 7/8 mutation
Unclassified
Although the significance of this categorization is still under research, the subtypes may indicate differential risk of hemorrhage or malignant transformation.
Pathologic diagnosis
Hepatic adenomas are, typically, well-circumscribed nodules that consist of sheets of hepatocytes with a bubbly vacuolatedcytoplasm. The hepatocytes are on a regular reticulin scaffold and less or equal to three cell thick. The histologic diagnosis of hepatic adenomas can be aided by reticulin staining. In hepatic adenomas, the reticulin scaffold is preserved and hepatocytes do not form layers of four or more hepatocytes, as is seen in hepatocellular carcinoma. Cells resemble normal hepatocytes and are traversed by blood vessels but lack portal tracts or central veins.
Treatment
Some authors feel that all hepatocellular adenoma should be resected, because of the risk of rupture causing bleeding and because they may contain malignant cells. Current recommendations are that all hepatic adenomas should be resected, as long as they are surgically accessible and the patient is a reasonable operative candidate. Patients with adenomas should avoid oral contraceptives or hormonal replacement therapy. Pregnancy could cause the adenoma to grow faster, so patients with hepatic adenomas should avoid pregnancy.
