Management of subcentimetre arterially enhancing and hepatobiliary hypointense lesions on gadoxetic acid-enhanced MRI in patients at risk for HCC

Objectives To investigate the significance of subcentimetre (≤1 cm) arterially enhancing and hepatobiliary hypointense lesions (SAELs) observed on gadoxetic acid-enhanced magnetic resonance imaging (MRI) of patients at risk of hepatocellular carcinoma (HCC). Methods A SAEL was defined as a subcentimetre hypervascular nodule exhibiting a hepatobiliary phase defect on gadoxetic acid-enhanced MRI. We included 52 SAELs from 46 patients in a HCC surveillance population. The HCC reference standard was pathologic confirmation or a nodule >1 cm with typical imaging features of HCC at follow-up imaging. The malignancy rate and HCC-favourable imaging findings of SAELs were evaluated. Results The malignancy rate among SAELs was 57.7% (30/52). At diagnosis, all SAELs that progressed to overt HCC were treatable with curative intention. Venous or late dynamic phase washout was more frequently observed with malignant SAELs than with benign SAELs (57.7% vs. 30.6%; P = 0.01). If SAELs exhibiting washout were considered as HCC, sensitivity, specificity, and positive predictive value was 83.3%, 50%, and 69.4%, respectively. Conclusion Among patients at risk of HCC, SAELs on gadoxetic acid-enhanced MRI exhibited high malignant potential. However, close observation may be an appropriate strategy for isolated SAELs. A washout appearance may be helpful for predicting malignancy. Key Points • Gadoxetic acid-enhanced MRI provides hepatobiliary phase (HBP) images. • Screening frequently detects subcentimetre arterially enhancing and hepatobiliary hypointense lesions (SAELs). • A majority of SAELs progressed to overt HCC within 2 years. • A venous-phase washout appearance correlated significantly with malignancy in SAELs.