Hepatocellular adenoma is a benign tumor derived from hepatocytes. It is a rare liver tumor mostly seen in women that usually remains solitary. The tumor is spherical, well demarcated and sometimes encapsulated. Pathologically, typical features of adenomas are a thin pseudocapsule, fatty contents, and intracellular glycogen. Differential diagnosis between hepatocellular adenoma and HCC can be difficult since both can be present with hemorrhage, fatty changes, and a capsule.
MRI appearance of a hepatocellular adenoma without (pre-contrast) and with Primovist®
Adenomas vary in signal from hypointense (dark areas) to hyperintense (bright areas/fat content) on T1-weighted (left-hand-side) and are hyperintense (bright areas) on T2-weighted images. However, hemorrhage and fatty alterations result in varying signal intensity. Like FNH, adenomas are typically hypervascular during the arterial phase. In contrast to FNH, a central scar is not observed.
In the dynamic phases, the liver-specific-phase, typical adenomas show an uptake of the agent and the lesion appears hyperintense (bright areas) in comparison to the surrounding parenchyma (right-hand-side). Both homogenous enhancement and heterogeneous hyperintensity with central isointense spots were reported.
- Precontrast: T1-weighted sequence, patient with two small adenomas
- After injection, T1-weighted, liver-specific phase
In cases regarding intratumoral or intraperitoneal hemorrhage, excision of the causative adenoma is recommended. Management of asymptomatic cases remains controversial. It is important to keep in mind that malignant transformation of hepatic adenomas has been documented and that bleeding into lesions of less than 5 cm has been reported. There is as of yet no consensus on the behavior of this lesion after the patient stops oral contraceptive therapy. Some authors have reported tumor regression in some of their patients; others have not. Some centers advocate surgical excision regardless of size and symptoms when considering the risk of hemorrhage and possible malignant transformation. For high-risk asymptomatic patients who have bilobar involvement or patients who will require major hepatic resection, a conservative approach with cessation of oral contraceptives and close follow-up is advised.