Most of the time, when a genetic screening is done of family members who may carry the genes that increase the risk of breast cancer, it is only the women of the family who are tested. However, it is also very important that the men in the family have the same genetic screening done as well. It turns out that the genes that increase the risk of a person developing breast cancer can be passed down paternally. This means that all members of a family need to be screened, in order to really determine risk factors.
Both females and males can carry the BRCA1 or BRCA2 gene mutations that increase the risk of developing breast cancer. It is a misconception that you can only inherit these genes from your mother, or from you female ancestors. Both the women and the men who carry this gene can pass it to their offspring. In other words, let's say that the women in your family had all been screened, and not one of them carries a mutated copy of either the BRCA1 or the BRCA2 gene. The assumption is that you cannot possibly have a mutated copy of those genes either, and that there is no chance of passing a mutated gene on to your children. However, since men can carry these genes too, it is possible that you have a mutated copy of one or both of these genes, which you can pass along to your children. This new finding explains how breast cancer seemed to come from out of nowhere in some families. It wasn't from nowhere, it was something that was passed down paternally.
In general, every woman has a 12% risk of developing breast cancer, and a 1.5% risk of developing ovarian cancer. Women who have a mutation on one of their BRCA genes have a much higher risk. These women have a 55% to 85% risk of getting breast cancer, and a 25% to 45% risk of having ovarian cancer.