Management of subcentimeter arterially enhancing and hepatobiliary hypointense lesions on gadoxetic acid-enhanced MRI in high risk patients for hepatocellular carcinoma

Abstract

Objectives: To investigate the significance of subcentimeter (≤1 cm) arterially enhancing and hepatobiliary hypointense lesions (SAELs) observed on gadoxetic acid-enhanced magnetic resonance imaging (MRI) in high risk patients for hepatocellular carcinoma (HCC). Methods: A SAEL was defined as a subcentimeter 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-favorable 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 high risk patients for 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.