Abstract: Objective To compare the change of Ki-67,HER-2,ER and PR before and after neoadjuvant chemotherapy in breast cancer tumor,and explore the relationship between the changes and clinical response rate.Methods 103 patients with breast cancer were included in this study who didn′t accept any therapy such as radiotherapy,chemotherapy and endocrine therapy before recruiting.All cases were diagnosed as local infiltrating ductal carcinoma or lobular carcinoma by 14G hollow needle biopsy.94 patients were operated after 4 cycles chemotherapy.Tumor tissues were formalin-fixed,paraffin-embedded.Immunohistochemical staining was employed to detect the expression of Ki-67,HER-2,ER and PR.The clinical response rate was evaluated by WHO criteria.Results 9 patients of 103 cases had metastasis after neoadjuvant chemotherapy,and 94 cases underwent surgery after chemotherapy treatment.Pre- and postoperative tumor biopsy tissue sections stained were compared.The level of expression of Ki-67,ER and PR changed significantly,and HER-2 before and after the chemotherapy was not significant.However,only the change of Ki-67 expression was significantly correlated with tumor response rate.Conclusion Ki-67 expression as an indicator may be used to predict the tumor response rate during neoadjuvant chemotherapy of clinical outcome in breast cancer patients.