Microscopic portal vein invasion is a powerful predictor of prognosis in patients with hepatocellular carcinoma who have undergone liver resection

Background and Objectives A recent study proposed simple classifications of microscopic vascular invasion (MVI): microscopic portal vein invasion (MPVI) and microvessel invasion (MI). We aim to validate these classifications of MVI. Methods This retrospective study consecutively enrolled 514 Barcelona Clinic Liver Cancer stage 0, A, and B naive hepatocellular carcinoma patients who underwent liver resection in our institution from 2011 to 2017. Results Among these 514 patients, 240 patients were classified as having no MVI at all (designated as no vascular invasion, NVI), 157 patients were classified as having MI only, and 117 patients were classified as having MPVI. The 5-year overall survival (OS) rate in the MI-only group was 83.3%, which was not significantly different from that of the NVI group (87.2%), p = .20. Using NVI as a reference, multivariate analysis showed that MI-only is not an independent variable associated with OS. The 5-year OS in the MPVI group was 59.2%, which was significantly lower than those for MI-only (p < .001) and NVI groups (p < .001). Using NVI as a reference, multivariate analysis showed that MPVI is an independent variable associated with OS (HR, 3.12; 95% CI, 1.80-5.40; p < .001). Conclusions The results of this study validate the simple MVI classifications to be clinically useful.