Characteristics and Early Recurrence of Hepatocellular Carcinomas Categorized as LR‐M: Comparison with Those Categorized as LR‐4 or 5

Background According to the Liver Imaging Reporting and Data System (LI‐RADS), the LI‐RADS category M (LR‐M), which are probably or definitely malignant but are not specific for hepatocellular carcinomas (HCCs), does not exclude HCCs. A gap in knowledge remains, including their characteristics and recurrence of HCCs categorized as LR‐M. Purpose To compare the characteristics of HCCs categorized as LR‐M with HCCs categorized as LR‐4 or LR‐5 (LR‐4/5) using the LI‐RADS version 2018 and evaluate the relationship of these categories with the risk of early recurrence after curative resections of single HCCs. Study Type Retrospective. Subjects Two hundred and eighty‐one patients (mean age, 57 years; 191 men and 90 women) who underwent curative resections for single HCCs and preoperative contrast‐enhanced MRI between 2015 and 2017. Field Strength/Sequence 3T Dual gradient‐echo T 1 WI with in‐ and opposed‐phase, turbo spin‐echo T 2 WI, diffusion‐weighted echo‐planar images, and three‐dimensional gradient‐echo T 1 WI before and after administration of contrast agent. Assessment MRI features according to the LI‐RADS version 2018 were evaluated and LI‐RADS category were assigned for each observation. Clinical, imaging, and histopathological features were compared based on LI‐RADS categorization. Early recurrence rates (<2 years) and associated factors were also evaluated. Statistical Tests Fisher's exact test, two‐sample t test after satisfying assumption of normality through Shapiro–Wilk test, Fleiss κ coefficient, Cox proportional hazards regression analysis, Kaplan–Meier method, and log‐rank test. Results Forty‐one HCCs (14.6%) were categorized as LR‐M and 240 HCCs (85.4%) were categorized as LR‐4/5. LR‐M HCCs showed poorer differentiation than LR‐4/5 HCCs. In the multivariate analysis, the LR‐M category was an independent predictor for early recurrence (hazard ratio, 1.904; 95% confidence interval, 1.024–3.542; P < 0.05). Early recurrence rates were significantly higher in patients with LR‐M HCCs than in patients with LR‐4/5 HCCs (32.0% vs. 18.4%, respectively, P < 0 05). Data Conclusion Compared to LR‐4/5 HCCs, LR‐M HCCs were associated with poorer tumor differentiation and higher early recurrence rates after curative resections of single HCCs. Level of Evidence : 3 Technical Efficacy Stage : 2