Experimental animal model plays a key role in preclinical cancer researchs. In this study, the authors have implanted human breast cancer cells BT-474 into subcutanous thigh of athymic nude mice by xenografts method. The nude mice developed tumors after 10 days of injection the BT-474 cell line with 106 cells per mouse and reached 617,2 + or - 87,8 mm3 in tumor sizes. The tumor patho-histological analysis indicated that the tumors contained the hyperchromasia, nuclear enlargement with atypia of the breast epithelial carcinoma.