Regardless of genetics or other risk factors you are not pre-destined to have breast cancer, though you may be more susceptible and thus would be well advised to take extra precautions.
In general, iodine with selenium and plenty of vitamin D3 (from the sun as much as possible) will greatly reduce your risk of getting breast cancer. So will cruciferous vegetables, a good whole-food derived multi-vitamin product, pomegranates, apples and olive oil. In my opinion, regular preventive doses of oleander extract will provide excellent protection against developing breast cancer. The best cancer fighting form of selenium, btw, is methylselenocysteine.
Here are some articles which may help further:
Broccoli and Brussels Sprouts Stop the Spread of Breast and Other Cancers Study Finds that Multivitamins and Calcium Slash Breast Cancer Risk
You can also check out this page for more articles and information about breast cancer prevention:
http://www.tbyil.com/cancer.htm