Imaging features of small hepatocellular carcinomas with microvascular invasion on gadoxetic acid-enhanced MR imaging

ObjectivesDetection of hepatocellular carcinomas (HCCs) before microvascular invasion (MVI) occurs is important due to the poor outcomes associated with MVI. We retrospectively investigated the imaging features of small HCCs with MVI on gadoxetic acid-enhanced MR imaging.MethodsFifty patients (40 men and 10 women; mean age, 54 years) with 58 surgically proven small (2 cm or less) HCCs were evaluated by gadoxetic acid-enhanced MRI. Signal intensities on imaging sequences and the presence of the typical dynamic enhancement pattern (arterial enhancement and washout) were assessed. Fisher's exact tests were performed to evaluate the relationships between the presence of MVI, tumor size, and imaging findings.ResultsNone of the 12 small HCCs with diameters of 1 cm or less had MVI, while 15 (33%) of the 46 small HCCs with diameters of 1.1-2.0 cm had MVI (p = 0.025, Fisher's exact test). Among the small HCCs with diameters of 1.1-2.0 cm, all HCCs with MVI showed the typical dynamic pattern and hyperintensity on T2- and diffusion-weighted images. Most HCCs (54 lesions, 93%) were hypointense on hepatobiliary phase images regardless of the presence of MVI.ConclusionsAll small HCCs with MVI showed typical dynamic pattern and hyperintensity on T2-weighted and diffusion-weighted images, while atypical dynamic pattern and size of less than 1 cm in diameter may suggest absence of MVI.