Breast Cancer Risk Factors

Breast cancer is the second most commonly diagnosed cancer in women. Understanding risk factors, knowing your own risk, and monitoring your breast health accordingly is key since early detection and intervention often mean the best outcomes.

Be sure to discuss any risk factors you may have for developing breast cancer with your primary care physician, gynecologist, oncologist, surgeon, or other healthcare providers to determine an appropriate screening routine.


While only about 5-10% of breast cancer can be linked to genetic mutations inherited from one’s mother or father, women with specific mutations of the BRCA1 and BRCA2 (or, “breast cancer”) genes have up to a an 87% risk of developing breast and up to a 44% risk of developing ovarian cancer.

If breast or ovarian cancer runs in your family, it may be hereditary. Women with a close, blood relative who has had breast or ovarian. You may consider genetic testing through the Hereditary Risk Assessment Program at Middlesex Hospital’s Comprehensive Breast Center.


You may be surprised to learn that 85% of breast cancers occur in women with no family history of breast cancer, and are due to genetic mutations that happen naturally during the aging process or from environmental and behavioral exposures throughout life. Non-hereditary risk factors for developing breast cancer can include: 


While men can develop breast cancer, women develop the disease about 100x more than men because their breast cells are constantly exposed to growth-promoting estrogen and progesterone hormones. 


Your risk of breast cancer increases as you age. 1 out of every 8 breast cancers is diagnosed in women under 45, while 2 of every 3 is diagnosed in women over 55. 

Personal History of Breast Cancer

Women who have had cancer in one breast are roughly 3x more likely to develop a new cancer in the other breast or another part of the same breast. New cancers developing are not the same as recurrence of a previous cancer. 

Race and Ethnicity

Breast cancer in women over the age of 55 is more commonly diagnosed in Caucasian, or white, women. But breast cancer in women under the age of 45 is more commonly diagnosed in African-American women. Women of Asian, Hispanic, and Native-American descent have a lower risk of developing breast cancer. 

Dense Breast Tissue

Simply having denser breast tissue can increase your risk of breast cancer—although many believe this is because it is harder to spot masses on mammograms. If you have dense breast tissue, you should discuss magnetic resonance imaging (MRI) as part of your screening routine with your physician. 

Benign Breast Conditions

The following benign breast conditions are associated with higher risk of developing breast cancer: fibrosis, mild or normal ductal hyperplasia, sclerosing and non-sclerosing adenosis, duct ectasia, Phyllodes tumor, single or several papillomas, fat necrosis, mastisis (infection of the breast), simple or complex fibroadenoma, radial scar, and atypical ductal or lobular hyperdplasia. 

Lobular Carcinoma in Situ

Also known as LCIS, or lobular neoplasia, is a condition in which cells that look like cancer cells are growing in the milk-producing glands of the breast, but are contained within the wall of the lobules. This is considered a non-invasive form of breast cancer. Women with this condition have a 7- to 11x increased breast cancer risk and should be get regular screening. 

Early Age of First Menstrual Period or Late Age for Menopause

Women who begin menstruating before the age of 12 and/or go through menopause after age 55 have a longer lifetime exposure to growth-promoting hormones, which can slightly increase the risk of breast cancer. 

Previous Chest Radiation

There is a significant increase in risk for developing breast cancer for women and men exposed to chest radiation before age of 40 for treatment of another cancer, such as Hodgkin’s and non-Hodgkin’s lymphoma. Risk is highest when exposure occurred before or during adolescence.  

Diethylstilbestrol Exposure

Between the 1940s and 1960s, some pregnant women at-risk for miscarriage where given a drug called diethylstilbestrol (DES), which can slightly increase the risk of breast cancer. 

Having Children

The risk of breast cancer is slightly higher in women who have not had children or had children after the age of 30. 

Use of Oral Contraception

Studies show a slight increase in breast cancer risk for women who have used oral contraceptive within the last 10 years. If you have one or more other risk factors, you should discuss them with your gynecologist in making decisions about using oral contraception. 

Hormone Therapy

Receiving combined hormone therapy after menopause or prolonged estrogen therapy (more than 10 years) can increase a woman’s risk of breast cancer. 

Alcohol Consumption

Risk of breast cancer is clearly linked to the amount of alcohol a woman consumes. Studies have shown that having one or more alcoholic beverages a day presents a slight increase, while consuming 2 to 5 a day presents a 1½x increase in risk. 

Weight and Physical Activity

Although the relationship between weight and breast cancer is complex, studies indicate that women who are overweight or obese have an increased risk of breast cancer, especially after menopause. The good news is that physical activity, 45 and 60 minutes for at least five days a week, will not only help maintain your weight, but can lower breast cancer risk up to 18%.

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