Objective To determine the expression of macrophage migration inhibitory factor (MIF)in different molecular subtypes of breast cancer and its clinical significance so as to detect the biological markers of different molecular subtypes of breast cancer.Methods We divided 100 breast cancer patients into four molecular subtypes by immunostaining:luminal subtype,HER-2(+)subtype,basal-like (BLs)subtype and normal breast-like (NBLs)subtype,and then compared the expression of MIF in the groups.We analyzed the associations of MIF-positive expression rate with age,menstruation,tumor size,auxiliary lymph node metastasis,histological type and grade,and clinical stage of the breast cancer patients.We also compared MVD level and 5-year overall survival rate between MIF-positive patients and MIF-negative ones.Results The positive expression of MIF was correlated with HER2(+)subtype breast cancer and auxiliary lymph node metastasis (P < 0.05 ).The patients with MIF-positive expression had a significantly higher level of MVD than those with MIF-negative expression (P < 0.05 ). Kaplan-Meier method showed that MIF-positive patients had a poor prognosis than MIF-negative ones (Log-rank=1 9.5 1 6,P = 0.000).Conclusion Breast cancer patients with MIF-positive expression may be mostly of HER2 (+)subtype,and tend to develop auxiliary lymph node metastasis.These patients have a significantly higher level of MVD and poor prognosis than those with MIF-negative expression.