Family history

I agree (as usual) with Melissa. In addition, some other factors to consider: a whole variety of genes can increase one's breast cancer risk (not just BRCA1 and BRCA2.) Different gene mutations in different genes could cause an increased risk of a different pattern of cancers that might happen at different ages. For example, BRCA1or 2 typically increases one's risk of breast and ovarian cancers, but mutations in other genes might affect one's risk of breast and thyroid cancer, as in the case of PTEN (Cowden's syndrome). Sometimes the risk of cancer might be increased in one age group and not another. The size of the increased risk can vary from gene to gene too: One gene mutation might cause a 50% increase in one's risk for a cancer, while another gene might increase the risk by only 10%.

Since this information is changing all the time, its good to check with your genetics counselor, just as Melissa said.