Abstract: Objective 　To study the clinicopathological characteristics, diagnosis, combined therapy and prognosis of accessory breast cancer. Methods 　17 patient s with accessory breast cancer were admitted from J anuary 1954 to October 2004 and their document s were ret rospectively analyzed. Results 　The 17 cases of accessory breast cancer account for 0. 1 % of all 19588 breast cancer cases for the same period.Follow-up to February 2005, 6 patients died of long-distance metastases and the other 11 patients were still alive. The 5 year survival rate was 35. 3 % (6/ 17) and less than 66. 8 % that of breast cancer, P <0. 05. Conclusion 　Accessory breast cancer is rare but aggressive. The diagnosis is mainly depended on postoperative pathology and imaging results. The combined therapy principle dominated by surgery should be followed and adjuvant therapy probably could improve the survival time.