Objective: Hepatocellular adenomas (HCAs) are divided into three subtypes according to genotype and phenotype. The two main subgroups are hepatocyte nuclear factor 1α (HNF1α)-inactivated HCA and inflammatory HCA. Specific imaging features of these subgroups of adenoma have been delineated with MRI. The aim of this study was to document the contrast-enhanced sonographic (CEUS) features specific for adenoma subtypes and to correlate them with MRI findings.
Materials and methods: We retrospectively analyzed data on 38 patients with HCA confirmed at pathologic examination in all cases. All cases were classified with MRI.
Results: HNF1α-inactivated HCA (n = 16) was found to have a homogeneous hyperechoic aspect at baseline gray-scale sonography, isovascularity or moderate hypervascularity with mixed filling in the arterial phase, and isoechogenicity in the portal and late portal venous phases. Homogeneous hyperechogenicity during B-mode sonography was the most specific pattern (sensitivity, 88%; specificity, 91%) and correlated with diffuse fat repartition observed on MR images obtained with chemical-shift sequences. In inflammatory HCA (n = 17) the association of arterial hypervascularity with centripetal filling, linear vascularities, peripheral rim of sustained enhancement, and central washout in the late venous phase was specific (sensitivity, 64%; specificity, 100%). Discrepancy between delayed washout during CEUS and sustained enhancement during MRI could be related to differences between gadolinium and microbubbles in diffusing in the interstitial spaces. In the five other HCA cases (four unclassified, one β-catenin activated) CEUS showed characteristics of benign hepatocellular tumors with no specific features.
Conclusion: HNF1α-inactivated HCA and inflammatory HCA had characteristic CEUS patterns. Delayed washout, an unusual finding in benign hepatic lesions, is of particular interest and was a characteristic of inflammatory HCA subtype.