• Gender - Women are at greater risk than men for developing the disease.
• Age - Risk increases with age.
• Genetics - Women with a family history of the disease are at a somewhat greater risk; women with a mutation in specific genes (BRCA1, BRCA2, PALB2, and others that have been identified and can be tested for) are at much greater risk including the risk of developing ovarian cancer. Men who carry the mutation in the BRCA2 gene are at a higher risk for prostate cancer.
• Having a personal history of breast cancer.
• Having a prior history of a breast cancer biopsy that revealed a precancerous lesion such as atypia (abnormal cells) or LCIS (lobular carcinoma in situ).
• A long window of estrogen exposure such as early onset of menstruation and/or late onset of menopause.
• Previous radiation such as chest radiation for Hodgkins disease.
• Ethnicity – White women have a higher risk of developing breast cancer than African-American women, but African-American women are more likely to die of the disease at a younger age possibly because of a more advanced stage at diagnosis or having a more aggressive type of the disease (triple negative). Asian, Native-American and Latina women have a lower risk of getting the disease and dying from it.
• Being overweight or obese (particularly important as you get older).
• Long term usage of post-menopausal hormone therapy (HRT).
• Excessive alcohol use, especially more than one drink per day.
• Lack of physical activity or exercise.
• Not having children or having children after the age of 35.
• Not breastfeeding. (Studies suggest long periods of breast feeding may reduce risk of premenopausal or earlier onset breast cancer).

However, it is important to note that having any or all of these risk factors does not mean that you will definitely get breast cancer. 75% percent of the women who develop breast cancer have no identifiable risk factors.
The connection between lifestyle factors and breast cancer, and between environmental toxins and breast cancer, is very important and many researchers are studying this. There is growing evidence that strong links exist. And now there is some evidence that lifestyle modifications may decrease one’s risk of developing a recurrence in those who have had breast cancer.