Objective: To determine the pathologic nature of non-hypervascular hypointense nodules (≥1 cm) on the hepatobiliary phase (HBP) of gadoxetic acid-enhanced magnetic resonance (MR) imaging and to describe the chronological changes of their imaging features on follow-up MR imaging.
Patients and methods: This retrospective study was approved by our Institutional Review Board and the requirement for informed consent was waived. 69 patients with 115 non-hypervascular HBP hypointense nodules (≥1 cm in diameter) in cirrhotic livers were enrolled. 67 nodules were histologically diagnosed (group 1) and 52 nodules were followed up with MR for at least 12 months (group 2); 4 nodules belonged to both groups. Two radiologists reviewed the initial and follow-up MR images to determine the size and signal intensities on unenhanced T1- and T2-weighted images, dynamic phases and HBP images in consensus. In addition, two pathologists reviewed the histologic findings including H&E staining and four kinds of immunohistochemical staining in group 1.
Results: In group 1, 73.1% (49/67) of nodules were hepatocellular carcinomas. In group 2, 32.7% (17/52) of nodules developed arterial hypervascularity on follow-up, and 78.8% (41/52) showed at least one of the three imaging features considered to indicate malignant changes during follow-up (mean 19 ± 10 months): increase in diameter by ≥5 mm (23/52, 44.2%), arterialization (17/52, 32.7%) and hyperintensity on T2-weighted images (18/52, 34.6%).
Conclusion: Our study results demonstrate that a significant proportion of non-hypervascular HBP hypointense nodules (≥1 cm in diameter) in patients with cirrhosis showed either malignant features on pathology (73.1%) or developed hypervascularity (32.7%) during follow-up.