Nodule-in-Nodule Imaging Pattern in Hepatocellular Carcinoma Treated by Transarterial Chemoembolization - a Multiparametric Magnetic Resonance Imaging Study

Background & Aims: Emerging minimally invasive treatments for hepatocellular carcinoma (HCC) can significantly improve a patient's prognosis, but they may alter the imaging features of the treated nodules. This study focuses on a series of patients presenting with a rare pathology, the nodule-in-nodule imaging pattern of HCC, analyzes the imaging features and discusses possible approaches for the diagnosis of tumoral recurrence. Method: Nine patients recruited over two years, having HCC with nodule-in-nodule imaging pattern on diagnosis, and treated by transarterial chemoembolization were monitored by magnetic resonance imaging (MRI). Nodule morphology, dynamic contrast behavior and size progression were followed in this study. Results: All patients showed tumor recurrence. In 7 nodules, a T2 weighted-imaging hyperintense signal of the HCC foci was found, with isointensity of the background nodule. Restricted diffusion within the HCC foci was found in 6 cases but with no statistical significance. Dynamic contrast images evaluation showed a "classical" enhancement pattern in five patients. All nodules had hypointense HCC foci in the hepatobiliary phase. Four patients demonstrated progressive disease according to the mRECIST criteria. Conclusions: Due to the particularly challenging nodule characteristics, the sensitivity in diagnosing HCC foci in these nodules is about 77% when using conventional imaging criteria related to nodule morphology. Contrast media uptake curves may be altered by changes in nodule hemodynamics caused by embolization. The diagnostic rate may be significantly increased by considering the tumoral size increase in follow-up studies and completing the study with a hepatobiliary phase using Acidum Gadoxeticum.