Objective To investigate the expression of HER2,matrix metalloproteinase 2 (MMP2),matrix metalloproteinase 9 (MMP9) and their relationships with clinicopathological characteristics and interactions among them in breast cancer.Methods The expression of HER2,MMP2,MMP9 was detected by immunohistochemical staining in 114 specimens of breast cancer patients.Results The positive rate of HER2,MMP2,MMP9 was 46.49%,78.95%,68.42% respectively.The expression of HER2 was correlated with lymph node metastasis.The expression of MMP2 and MMP9 in patients with tumor size 2 cm or lymph node metastasis was significantly higher than that in the patients with tumor size ≤2 cm or without lymph node metastasis,and the expression of MMP2 was correlated with clinical stage.The expression of HER2 was also correlated with the expression of MMP2 and MMP9.Conclusion The expression of HER2,MMP2 and MMP9 may indicate stronger invasion and metastasis potential of breast cancer.The expression of these three proteins may play a synergic effect in the procedure of invasion and metastasis of breast cancer.