Hepatic adenoma: MR characteristics and correlation with pathologic findings.

OBJECTIVE: The purpose of this study was to describe the MR appearance of hepatic adenomas and correlate the MR imaging features with pathologic findings.
MATERIALS AND METHODS: MR examinations were performed in 14 patients with 66 hepatic adenomas. The diagnosis of hepatic adenoma was proved pathologically in nine patients (22 lesions). In five other patients (44 lesions), who had type I glycogen storage disease and were known to be at risk for hepatic adenomas, the diagnosis was established by repeated sonographic examinations that showed stability, reduction, or resolution of hepatic tumors. T1- and T2-weighted spin-echo MR images obtained at 1.5 T were retrospectively reviewed for the signal intensity of the lesions relative to liver, the signal pattern, the presence of a capsule, and the presence of hemorrhage. Histopathologic specimens (22 lesions) were reviewed for fat content (graded 0-3), the presence of a capsule, and the presence of hemorrhage.
RESULTS: On T1-weighted images, 51 (77%) of 66 lesions were hyperintense, 11 (17%) were hypointense, and four (6%) were isointense with respect to liver. On T2-weighted images, 49 (74%) of 66 lesions were hyperintense, 12 (18%) were isointense, and five (8%) were hypointense. Sixty-one (92%) of 66 lesions were heterogeneous. Eleven (17%) of 66 lesions were hemorrhagic. Of the 22 lesions reviewed histopathologically, 17 were hyperintense on T1-weighted images; 15 of these had a fat content of grade 2 or 3 and two had hemorrhage. All 15 lesions that had a fat content of grade 2 or 3 were hyperintense on T1-weighted images.
CONCLUSION: Hepatic adenomas have a variable MR appearance but most often are hyperintense with respect to liver on T1- and T2-weighted images. The high signal intensity often relates to the increased fat content of these lesions.