Familial risks for the development of breast cancer are very much in the news, but probably over rated.
We need to differentiate between familial risk; something that may run in families because they share the same environment and background; and genetic risk which is related to inherited factors.
Genes can increase the chance of getting breast cancer, and have to be handed down by a blood relative. The chance of getting such a gene depends first a parent having the gene, which is unusual, and giving the gene to an offspring, which is 50:50.
Having a predisposing gene does not mean the individual will get breast (or ovarian cancer), but increase the lifetime chance to about 50 to 80% from the population average of about 12%. (Therefore a relative risk of about 4 to 10).
The chances of having a gene therefore depend on the chances of a first degree relative (mother father sister or daughter) having an affected gene, and this is where risk prediction comes in. In general terms the more relatives having breast cancer and the younger they are at diagnosis, the greater the chance of there being a gene in the family.
We cannot remove genes, and consequently if there is a high risk, the approach tends to be increased surveillance with mammography.