Impact of MVD and HIF-1α, VEGF and MMP-2 expression on patient overall survival (log-rank test) is shown. (A) The log-rank test revealed a significantly shorter overall survival rate in patients with tumors with a high MVD (P=0.018). Kaplan-Meier analyses indicated that there were no significant differences in the survival rates between (B) the high and low HIF-1α expression groups, (C) the VEGF-positive and VEGF-negative groups or (D) the high and low MMP-2 expression groups (P=0.223, P=0.740 and P=0.451, respectively). HIF-1α, hypoxia-inducible factor-1α; VEGF, vascular endothelial growth factor; MMP-2, matrix metalloproteinase-2; MVD, microvessel density.