Microvascular invasion (MVI) is a poorer prognostic predictor for small hepatocellular carcinoma

BACKGROUND: Small hepatocellular carcinoma (SHCC) is a special type of hepatocellular carcinoma with the maximum tumor diameter ≤ 3 cm and excellent long-term outcomes. However, the prognostic factors for SHCC remain controversial. The purpose of this study is to clarify the predictive factors of SHCC. METHODS: The study population consisted of 458 patients underwent hepatectomy for single SHCC between January 2006 and December 2008. Clinical data (included age, gender, virus infection, serum alfa-fetoprotein level, cirrhosis, capsule, border), histopathologic features (included differentiation, morphology subtype, microvascular invasion, tumor infiltrative lymphocytes (TIL), inflammatory injury grade and fibrosis stage of surrounding liver), were evaluated to identify prognostic factors influencing SHCC patients’ survival and microvascular invasion. RESULTS: There were 384 males (83.8%) and 74 (16.2%) females with median ages of 52 years. The median progression-free survival (PFS) and overall survival (OS) durations were 53 and 54 months, respectively. About 91.9% (n = 421) SHCC were infected by Hepatitis B. One hundred forty-seven of the 446 (33.0%) patients with pre-operation serum AFP level record had serum alfa-fetoprotein (AFP) level ≥ 200 ug/ml and 178 of the 280 (63.8%) patients with post-operation serum AFP level record had AFP level ≥ 20 ug/ml. Liver cirrhosis was present in 411 cases (89.7%), while 434 (97.3%) tumors had clear border, and 250 (55.6%) tumors were encapsulated. MVI was identified in 83 patients (18.1%). In univariate analysis, a significant association between the presence of MVI and shortened PFS and OS was found (p = 0.012, 0.028, respectively). Histological differentiation had strong relationship with MVI (p = 0.009), in terms of MVI was more easily presented in patients with worse histological differentiation. In patients with MVI, worse survival was correlated with female patients, patients with G2 or G3 histological differentiation, pre-operation serum AFP level ≥ 200 ug/ml or post-operation serum AFP level ≥ 20 ug/ml, and TIL ≥ 50/HPF. CONCLUSIONS: MVI is an independent poorer prognostic factor for PFS and OS of single SHCC patients. Tumor histological differentiation was closely related with MVI.