In developed countries, breast cancer affects about one in ten women, and in many of these countries the disease is on the increase. But, whatever the reason (or reasons) for the rise in their occurrence, we also know that between 5% and 10% of breast cancers are due to an inherited defect that affects the BRCA1 or BRCA2 genes.
十分之一的发达国家女性患有乳腺癌，并且这种疾病在多数这些国家中正呈上升趋势。但是，无论是哪个（或哪些）原因导致了目前这种趋势，我们都知道5%至10%的乳腺癌患者是由于BRCA1或BRCA2基因感染了遗传性缺陷。