BRCA1 and breast cancer: Since the differing results of studies on breast cancer in BRCA1 carriers undergoing prophylactic salpingo-oophorectomy came from multi-center, multi-national trials performed in various countries: USA, Canada, Netherlands, France, Norway, Spain, Australia and New Zeeland, we believe that it is necessary to examine molecular background in all populations, particularly for such a common malignancy as breast cancer.