Abstract: Objective To study the prognostic affection of micrometastases in axillary lymph nodes of primary breast cancer. Methods Forty-five cases of stage Ⅰ to Ⅱ primary breast cancer in which axillary lymph nodes were metastatic negative by routine pathological examination were divided into two groups,one is died (25 cases),the other is alive (20 cases) through more than 10 years of follow-up.Sup-serial sections and immunohistochemistry techniques were used to re-examined the whole lymph nodes for micrometastases detection.Monoclonal antibody cytokeratin 19 was used as the primary reagents to identify tumor cells in lymph nodes. Results Immunostaining positive tumor cells were found in 13 cases of died group,while no positive tumor cell was found in alive group (P<0.01). Conclusion Micrometastasis can affect patient s'prognosis significantly.Micrometastases detection in lymph nodes of primary breast cancer is valuable theoretically and practically.