Abstract: Objective: To study the role and clinical significance of heparanase(Hpa) in the progress of invasive ductal carcinomas of the breast.Methods: Hpa expression in 14 cases of fibroadenomas and 81 cases of invasive ductal carcinomas of the breast was examined by PV-9000 immunohistochemistry analysis.Its correlation with clinic-pathological parameters in the carcinomas of the breast was also studied.Results: The positive expression ratio of Hpa in the tissues of invasive ductal carcinomas of the breast was 72.96%,which was significantly higher than that in fibroadenomas(P<0.005);Hpa expression was correlated with tumor's size,pTNM stage,histological grade and lymph node metastasis(P<0.005),but was not significantly correlated with patients' menstruation status or age(P>0.05).Conclusions: Hpa may accelerate the growth,invasion and metastasis of carcinomas of the breast.It reflects the biological characteristics of carcinomas of the breast to some degree.