The Significance of Classifying Microvascular Invasion in Patients with Hepatocellular Carcinoma

Background. Microvascular invasion (MVI) has been recognized as a risk factor for outcome following curative resection in hepatocellular carcinoma (HCC). Because MVI can range from few to many invaded vessels, we evaluated the significance of MVI classification in this study. Methods. Between January 1995 and December 2010, 207 consecutive patients who underwent curative resection for HCC within Milan criteria were included in this retrospective study. Patients were classified into mild and severe MVI groups based on the number of vessels invaded. This study evaluated whether MVI classification can help to predict recurrence and survival after curative resection. Results. Of the total 207 patients, 103 (50 %) patients had no detectable MVI, whereas 59 (28 %) had mild MVI, and 45 (22 %) had severe MVI. Recurrence-free survival rates at 2 years for patients without MVI, with mild MVI, and severe MVI were 75.9, 47.2, and 32.7 %, respectively. Patients with severe MVI experienced a high frequency of fatal recurrence, such as multiple tumors, macroscopic vascular invasion, and extrahepatic metastasis after curative resection. Multivariate analysis revealed age, number of tumors, mild MVI, and severe MVI as independent predictors of recurrence-free survival. Disease-specific survival rates at 5 years for patients without MVI, with mild MVI, and severe MVI were 91.5, 70.4, and 51.4, respectively. Multivariate analysis also revealed cirrhosis, tumor size, mild MVI, and severe MVI as independent predictors of disease-specific survival. Conclusions. We demonstrated that MVI classification can stratify HCC patients by different patterns of recurrence and risk of survival after curative resection.