Breast cancer risk is higher among women whose close blood relatives have this disease.
Having one first-degree relative (mother, sister, or daughter) with breast cancer approximately doubles a woman's risk. Having two first-degree relatives increases her risk about five-fold.
Altogether, about 20% to 30% of women with breast cancer have a family member with this disease. This means that most (70% to 80%) women who get breast cancer do not have a family history of this disease. And certainly not all women with a family history get breast cancer.