Objectives

1) Understand the new and prior classification schemes for hepatocellular adenoma (HCA) subtypes

2) Appreciate how this new classification affects clinical management and relates to underlying patient risk factors

3) Recognize known and unknown MR imaging findings for each HCA subtype, with a focus on hepatobiliary-specific contrast agents and quantitative imaging

4) Correlate MR imaging findings with histologic findings

5) Implications for future research

Background

HCAs are benign liver tumors that have undergone several changes in classification schemes. They were originally thought to reflect a single entity but in 2006, were reclassified into 4 subtypes based primarily on histologic findings: inflammatory, hepatocyte nuclear factor (HNF)-1α-mutated, β-catenin activated, and unclassified. More recently, they were reclassified into 8 subtypes based on gene expression. HCA subtype is important as it guides clinical management, which may range from surgical resection for those with a higher risk of life-threatening hemorrhage and malignant degeneration or imaging surveillance for lower risk subtypes.

Imaging findings OR Procedure findings

The majority of HCAs are hypointense on the hepatobiliary phase, but their signal intensity relative to liver varies depending on the subtype. Hepatobiliary phase signal intensity is predominantly mediated by OATP1B1/B3, which is responsible for Gd-EOB-DTPA transport into the hepatocyte. OATP1B1/B3 expression appears to be a part of the Wnt/β-catenin signalling pathway and may explain why β-catenin activated HCAs retain Gd-EOB-DTPA. HNF-1α is a global transcription factor that governs OATP1B1/B3 expression and may explain why HNF-1α-mutated HCAs show the least Gd-EOB-DTPA uptake.

Conclusion

MR imaging features correspond to histologic findings and may suggest a particular subtype.