Gender.  Being a woman is the most significant risk factor for developing breast cancer.  Although men can get breast cancer, too, women’s breast cells are constantly changing and growing, mainly due to the activity of the female hormones estrogen and progesterone,  This activity puts them at must greater risk for breast cancer.  Age.  Simply growing older is the second biggest risk for breast cancer.  From age 30 to 39, the risk is 1 in 228, or .44%.  That jumps to 1 in 29, or just under 3.5%, by the time you are in your 60s.  Family history of breast cancer.  If you have a first-degree relative (mother, daughter, sister) who has had breast cancer, or you have multiple relatives affected by breast or ovarian cancer (especially before they turned age 50), you could be at higher risk of getting breast cancer.  Personal history of breast cancer.  If you have already been diagnosed with breast cancer, your risk of developing it again, either in the same breast or the other breast, is higher than if you never had the disease.  More risk factors to come.

Source:  NCI  2019