Abstract: Objective To explore the value of GCDFP-15 (gross cystic disease fluid protein-15) and mammaglobin as specific molecules involved in ovary cancer resulted from metastasis of breast cancer. Methods Data from Nov. 1995 to Dec. 2007 were undergone retrospectively analysed. Twenty patients of metastatic ovarian cancer (MOC)from breast cancer and 10 patients of primary epithelial ovarian cancer (EOC) with a history of breast cancer were obtained. Immunohistochemical method was employed to detect the more diagnostic value of the specific molecules in these patients. Results In MOC patients, the average age was 45 years-old(ranged from 28 to 53 years old), 9 of the 12 cases were incidental findings at therapeutic oophorectomy. Twelve patients (100%) had extraovarian metastases at the diagnosis of ovarian metastasis. The ovaries were grossly normal in 9(75%) cases. The preoperative imaging examinations including computed tomography (CT) and ultrasonography (US) were negative in 9 patients (75%) and the diagnosis of ovarian metastasis has been neglected in 9 patients (75%) before oophorectomy. Ovarian metastases were bilateral in 81.81% patients (9/11). The positive expression of GCDFP-15 and mammaglobin protein in the tissues of MOC were significantly higher than those in the EOC(75vs.0,P<0.001; 50％ vs.0,P＝0.033). The positive expression of WT1 and CA125 protein in the tissues of MOC were significantly lower than those in the EOC (16.66％vs.80％,P＝0.008; 16.66％vs.90％,P＝0.002). Of the serum markers, the preoperative level of serum CA153 was not different between the two groups（128.6u/ml of patients with MOC vs.56.48Μu/ml of patients with EOC，P＝0.315）. The serum CA125 level rose in 50% MOC patients (6/12) with a mean value of 81.88u/ml （47.15～966.9)u/ml），and in 100% EOC patients while the mean value was 1073u/ml （134.3～1821)u/ml）(P＝0.003). The metastatic ovarian tumors, as measured preoperatively by ultrasonography (US) or CT, were smaller <4cm, (0~8.3)cm than the primary tumors 10.2cm, (5~26)cm (P<0.001). Bilateralism and metastases in abdominal cavity were more common among patients with MOC(P<0.001). Conclusion Ovary metastases from breast cancer are generally seen in the younger premenopausat patients with extraovarian metastases. The tumor sizes are generally small and are incidental found at therapeutic oophorectomy. An immunohistochemical panel consisting of GCDFP-15, mammaglobin, WT1 and CA125 is effective in distinguishing most of breast from ovarian cancers and is useful to find the small and tiny ovary metastases. Small bilateral ovarian enlargements and minor serum elevation of CA125 titers in patients with initial stage IV breast cancer, suffering from multiple metastatic disease, are likely to illustrate MOC.