Hyperintense nodule-in-nodule on hepatobiliary phase arising within hypovascular hypointense nodule: Outcome and rate of hypervascular transformation

Purpose: To investigate the clinical implications and natural history of observations showing a nodule-in-nodule architecture on hepatobiliary phase (HBP) in a cirrhotic population. Method: This is an IRB-approved retrospective study conducted in a single institution. We identified 20 patients (11 men and 9 women, mean age 71 years, range 51-83 years) who had a hyperintense nodule on HBP arising within a larger HBP-hypointense nodule without arterial phase hyperenhancement (APHE) at gadoxetate disodium-enhanced MRI. Size and signal intensity of the nodules were evaluated in all sequences, along with the evolution of the nodules at serial MRI studies. Results: Twenty-four nodules were analyzed in 20 patients. Mean diameter of the inner hyperintense nodule on HBP was 1.1 cm (range 0.6-1.8 cm) and that of the outer hypovascular hypointense nodule was 2.1 cm (range 1.2-4.1 cm). All intranodular foci were hyperintense on HBP and showed a typical pattern for hepatocellular carcinoma (HCC) with APHE and washout on portal venous phase (PVP) (n= 11, 46%), washout only (n= 7, 29%) or APHE with no washout (n= 6, 25%). The hyperintensity on 3-, 5- and 10-minute phases was seen in 21%, 58% and 83% of the nodules, respectively. In twelve out of sixteen (75%) nodules with subsequent imaging available the hyperintensity on HBP occurred before either the appearance of APHE or washout on PVP. Conclusions: HBP-hypointense nodules without APHE may contain a hyperintense smaller nodule-in-nodule on HBP that can precede the appearance of either APHE or washout on PVP.