Evolution of Hypointense Hepatocellular Nodules Observed Only in the Hepatobiliary Phase of Gadoxetate Disodium-Enhanced MRI

OBJECTIVE. We sought to determine whether hypointense hepatocellular nodules observed in the hepatobiliary phase of MRI enhanced with gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (gadoxetate disodium) progress to hypervascular hepatocellular carcinoma. MATERIALS AND METHODS. Gadoxetate disodium-enhanced MRI was repeated for 30 patients with 49 nodules determined to be hypointense in the hepatobiliary phase but nonenhancing in the arterial phase of dynamic MRI. The correlation between characteristics of hypointense nodules with slightly or markedly low signal intensity relative to surrounding liver parenchyma and their progression to hypervascular hepatocellular carcinoma was analyzed in cirrhotic livers. All patients underwent angiography-assisted CT before MRI. The rate of progression to classic hepatocellular carcinoma was calculated by the Kaplan-Meier method. RESULTS. The overall 6- and 12-month cumulative incidences of vascularization were 27.6% and 43.5%. The 6- and 12-month cumulative incidences of vascularized nodules with a maximum diameter 15 mm or greater were 43.3% and 77.3% and a maximum diameter less than 15 mm were 16.9% and 16.9%. The difference between these incidences was significant (p = 0.0147). CONCLUSION. Hypointense nodules with a maximum diameter of at least 15 mm often become hypervascular. Therefore, patients with hypointense nodules characterized by a maximum diameter of 15 mm or greater should be observed carefully because of the high incidence of vascularization.