Abstract: Objective: To discuss the clinical significance and relationship between expression of fibronectin mRNA and metastasis of breast cancer. Methods: The fibronectin mRNA expression of 30cases with paring lymph-node metastatic carcinoma and 116 with primary breast cancer were detectedand the relationship between the fibronectin mRNA expression and clinicopathologic factors of breast cancer was analyzed using fluorescent-quantitative RT-PCR. Results: FN mRNA expression in 30metastatic lymphnode was lower than in primary breast cancer (P<0.05). The mRNA expression of FNin the tumor over 5cm was lower than in those less or equal to 5cm (P<0.05). The FN mRNA expres-sions in stageⅠ and were lower than in stage Ⅱ (P<0.05). The mRNA expression of FN in more than 4lymph nodes positive was lower than in lymph node 1-3 positive (P<0.05). The mRNA expressions of FN in ER and PR positive were higher than in ER and PR negative. The FN mRNA expression was ir-related with tissue grade, pathologic type, Her-2 and CA153. Conclusion: FN mRNA expression isup-regulated in the clinical early stage of the lesion and the early stage of lymph-node metastasis, andis down-regulated with the progression of tumors. FN mRNA expression is related with the metastasis of breast cancer.