From the Research
Hepatic adenomas on MRI and CT scans have characteristic imaging findings that help differentiate them from other liver lesions, with the most recent and highest quality study 1 guiding the diagnosis and management. On CT, hepatic adenomas typically appear as well-defined, homogeneous lesions that are hypodense or isodense on unenhanced images. During the arterial phase of contrast enhancement, they show avid homogeneous enhancement due to their predominant arterial blood supply. In the portal venous and delayed phases, they become isodense or slightly hypodense compared to surrounding liver parenchyma. On MRI, hepatic adenomas are usually hyperintense on T1-weighted images due to the presence of fat or glycogen and slightly hyperintense on T2-weighted images, as shown in a study from 2. After gadolinium administration, they demonstrate similar enhancement patterns as seen on CT with strong arterial enhancement and becoming isointense or slightly hypointense on delayed phases. Specific MRI findings include:
- The presence of intralesional fat (detected on chemical shift imaging)
- Absence of a capsule
- Lack of central scar
- Hemorrhage within adenomas appears as high signal on T1-weighted images Subtypes of hepatic adenomas (HNF1α-mutated, inflammatory, β-catenin-mutated) may show slightly different imaging characteristics, with inflammatory adenomas often showing persistent enhancement on delayed phases and a "atoll sign" on T2-weighted images, as discussed in 1. These imaging features help distinguish hepatic adenomas from focal nodular hyperplasia, hepatocellular carcinoma, and other liver lesions. The management of hepatic adenomas should be guided by the most recent and highest quality evidence, with surgical resection considered in asymptomatic patients who are male, have an adenoma ≥5 cm in diameter, or have the β-catenin-activated subtype due to an increased risk of hemorrhage and/or malignant transformation, as recommended in 1.