New research has discovered some abnormal genes that are associated with an increased risk of breast cancer. These genes can be passed genetically from mother to child. Only 1 in 10 women with breast cancer have an abnormal gene, however. Even if you have an abnormal gene, it does not mean you will get breast cancer.
Breast cancer due to an inherited gene abnormality tends to happen at an early age (under 40), in multiple relatives, and in one or both breasts (but usually not at the same time). The abnormal gene also is associated with an increased risk of ovarian cancer.
On the other hand, the majority of women who get breast cancer do not have a history of breast cancer in their family.