Hepatocellular adenoma: MR imaging features with pathologic correlation.

OBJECTIVE: The purpose of this study was to describe the MR imaging characteristics of hepatic adenomas and to correlate these features with pathologic findings.
MATERIALS AND METHODS: Sixteen patients from four institutions who had 31 hepatocellular adenomas underwent MR imaging with T1- and T2-weighted pulse sequences at 1.5 T. Dynamic gadolinium-chelate-enhanced gradient-recalled-echo (GRE) MR imaging was done in eight patients with 15 lesions. Twenty-three lesions in 15 patients were confirmed by surgical excision. MR images were retrospectively reviewed by three experienced radiologists for signal intensity of lesions relative to liver, heterogeneity, contrast enhancement, and presence of signs of histopathologic correlates. These imaging findings were then compared with histopathologic findings.
RESULTS: Nearly all (29 of 31 lesions) hepatocellular adenomas showed heterogeneous signal intensity on MR images. Most (19/31) were predominantly hyperintense on proton density- or T2-weighted images; the predominant signal intensity on T1-weighted images varied. Thirteen of 15 lesions showed early arterial enhancement relative to liver on dynamic GRE MR images. MR imaging was most successful in showing intratumoral hemorrhage (10 of 12 histopathologically proven lesions), large intratumoral vessels (five of five), fatty change (three of six), and peliosis (three of three cases). In two lesions, capsules (one of five) and central scars (one of three) were detected.
CONCLUSION: Hepatocellular adenomas have a highly variable appearance on MR images because of their varied histologic appearances. Although no definitive MR imaging signal or structural characteristics can be identified, tumor heterogeneity, particularly when related to hemorrhage, and early arterial enhancement can suggest a diagnosis of hepatocellular adenoma in the proper patient population.