Subcentimeter hypervascular nodule with typical imaging findings of hepatocellular carcinoma in patients with history of hepatocellular carcinoma: natural course on serial gadoxetic acid-enhanced MRI and diffusion-weighted imaging

Objectives: To evaluate the natural course of subcentimeter hypervascular nodules at high risk for developing into hepatocellular carcinomas (SHNHR) using serial magnetic resonance imaging (MRI) in patients with a history of hepatocellular carcinoma (HCC). Methods: An SHNHR was defined as a subcentimeter hypervascular nodule having typical imaging findings of HCC on gadoxetic acid-enhanced MRI and diffusion-weighted imaging. We included 39 patients with 46 SHNHRs (mean size ± standard deviation, 6.1 ± 1.6 mm; range, 3.2 – 9.0 mm). Overt HCC was defined as pathology proven HCC or a nodule larger than 1 cm with typical imaging findings of HCC. The cumulative rate and the independent predictive factors for progression to overt HCC were evaluated. Results: The median follow-up period was 139 days (range, 64 – 392 days). The cumulative progression rate to overt HCC at 3, 6, 9, and 12 months was 13.9 %, 61.7 %, 83.2 %, and 89.9 %. The initial size of SHNHR was a significant predictor of progression to overt HCC, with an optimal cut-off value of 5.5 mm. Conclusion: The progression rate of SHNHR to overt HCC within 12 months was high (89.9 %) in patients with history of HCC. The initial size of SHNHR was an important predictor for progression to overt HCC. Key Points: • Most SHNHRs (89.9 %) progressed to overt HCCs within 12 months. • Initial size was an important predictor for progression to overt HCCs. • The optimal cut-off value for initial nodule size was 5.5 mm.