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.