Abstract: Objective Detect the expression of metadherin（MTDH）mRNA and protein and investigate the role of MTDH in the development of breast cancer. Metheds Detect the expression of MTDH protein and mRNA in breast cancer and normal breast tissue by Western bloting and RT-PCR. Analyze the relatives of MTDH protein and clinicothological parameters. Results The positive rate of MTDH protein were significantly higher in cancer tissues than that in normal breast tissues(P＜0.05). The expression of MTDH in cancer tissue were correlated with lymphnode metastasis(P＜0.05) and were not correlated with TNM stage and differentiation grade. The positive rate of MTDH mRNA were significantly higher in cancer tissues than that in normal breast tissues（P＜0.05）; The expression of MTDH mRNA were significantly higher in cancer tissues than that in normal breast tissues(P＜0.05). Conclusion The carcinogenesis , invasion and metastasis of breast cancer may be related to overexpression of MTDH protein and mRNA.

Key words: Breast tumor, MTDH, Protein, mRNA