Objective To investigate the expression of macrophage migration inhibitory factor (MIF) in breast cancer and to analyze the relationship between MIF expression and clinicopathological features,tumor microvessel density(MVD),and prognosis.Method The expression of MIF in 121 samples of breast cancer,20 samples of breast benign tumors,and 20 samples of normal breast tissues were examined by tissue microarray using immunohistoehemistry.The values of MVD in the breast cancer samples were examined by immunohistochemistry using anti-CD34.The association of MIF expression with the clinicopathological characteristics and prognosis was further analyzed using the computer software Statistical Package for the Social Sciences 13.0.Results The MIF positive expression rate of the breast cancer tissues Was 29.8％,significantly higher than those of the benign tumors and normal breast tissue (P=0.031).MIF expression rate was positively correlated with the expression of interleukin-8(IL-8)(P=0.014),MVD (P=0.043),and HER-2 (P=0.030).The survival rate of the patients with positive MIF expression in breast tissues was 80.6％.not significantly different from that of the negative MIF expression group (87.1％,P=0.171),however,the tumor-free survival rate of the MIF positive expression group was 72.2％,significantly lower than that of the MIF negative group (87.1％,P=0.029).Conclusion MIF may predict a poor prognostic factor for human breast cancer,and may be used as a novel molecular marker to predicate the progression of breast cancer.Through promoting the secretion of IL-8,MIF participates in the angiogenesis in breast cancer.