Breast Cancer Risk Factors You Cannot Change

A risk factor is anything that affects your chance of getting a disease, such as breast cancer. But having a risk factor, or even many, does not mean that you are sure to get the disease.

Some risk factors for breast cancer are things you cannot change, such as being a woman, getting older, and having certain gene changes. These make your risk of breast cancer higher.

Being a woman

Simply being a woman is the main risk factor for breast cancer. Men can get breast cancer, too, but this disease is about 100 times more common in women than in men.

Getting older

As you get older, your risk of breast cancer goes up. Most breast cancers are found in women age 55 and older.

Certain inherited genes

About 5% to 10% of breast cancer cases are thought to be hereditary, meaning that they result directly from gene defects (called mutations) passed on from a parent.

BRCA1 and BRCA2: The most common cause of hereditary breast cancer is an inherited mutation in the BRCA1 or BRCA2 gene. In normal cells, these genes help make proteins that repair damaged DNA. Mutated versions of these genes can lead to abnormal cell growth, which can lead to cancer.

If you have inherited a mutated copy of either gene from a parent, you have a higher risk of breast cancer.
On average, a woman with a BRCA1 or BRCA2 gene mutation has about a 7 in 10 chance of getting breast cancer by age 80. This risk is also affected by how many other family members have had breast cancer. (It goes up if more family members are affected.)
Women with one of these mutations are more likely to be diagnosed with breast cancer at a younger age, as well as to have cancer in both breasts. They also have a higher risk of developing some other cancers, mainly ovarian cancer.
In the United States, BRCA mutations are more common in Jewish people of Ashkenazi (Eastern Europe) origin than in other racial and ethnic groups, but anyone can have them.

Changes in other genes: Other gene mutations can also lead to inherited breast cancers. These gene mutations are much less common, and most of them do not increase the risk of breast cancer as much as the BRCA genes.

ATM: The ATM gene normally helps repair damaged DNA (or helps kill the cell if the damaged can't be fixed). Inheriting 2 abnormal copies of this gene causes the disease ataxia-telangiectasia. Inheriting one abnormal copy of this gene has been linked to a high rate of breast cancer in some families.
TP53: The TP53 gene gives instructions for making a protein called p53 that helps stop the growth of abnormal cells. Inherited mutations of this gene cause Li-Fraumeni syndrome. People with this syndrome have an increased risk of breast cancer, as well as some other cancers such as leukemia, brain tumors, and sarcomas (cancers of bones or connective tissue). This mutation is a rare cause of breast cancer.
CHEK2: The CHEK2 gene is another gene that normally helps with DNA repair. A CHEK2 mutation can increase breast cancer risk about 2-fold.
PTEN: The PTEN gene normally helps regulate cell growth. Inherited mutations in this gene can cause Cowden syndrome, a rare disorder that puts people at higher risk for both non-cancer and cancer tumors in the breasts, as well as growths in the digestive tract, thyroid, uterus, and ovaries.
CDH1: Inherited mutations in this gene cause hereditary diffuse gastric cancer, a syndrome in which people develop a rare type of stomach cancer. Women with mutations in this gene also have an increased risk of invasive lobular breast cancer.
STK11: Defects in this gene can lead to Peutz-Jeghers syndrome. People affected with this disorder have pigmented spots on their lips and in their mouths, polyps (abnormal growths) in the urinary and digestive tracts, and a higher risk of many types of cancer, including breast cancer.
PALB2: The PALB2 gene makes a protein that interacts with the protein made by the BRCA2 gene. Mutations in this gene can lead to a higher risk of breast cancer.

Mutations in several other genes have also been linked to breast cancer, but these account for only a small number of cases.

Genetic testing: Genetic testing can be done to look for mutations in the BRCA1 and BRCA2 genes (or less commonly in other genes such as PTEN or TP53). While testing can be helpful in some cases, not every woman needs to be tested, and the pros and cons need to be considered carefully.

If you’re thinking about genetic testing, it’s strongly recommended that you first talk to a genetic counselor, nurse, or doctor who can explain these tests. It’s very important to understand what genetic testing can and can’t tell you, and to carefully weigh the benefits and risks of genetic testing before these tests are done. Testing costs a lot and might not be covered by some health insurance plans.

Having a family history of breast cancer

It’s important to note that most women (about 8 out of 10) who get breast cancer do not have a family history of the disease. But women who have close blood relatives with breast cancer have a higher risk:

Having a first-degree relative (mother, sister, or daughter) with breast cancer almost doubles a woman’s risk. Having 2 first-degree relatives increases her risk about 3-fold.
Women with a father or brother who have had breast cancer also have a higher risk of breast cancer.

Overall, less than 15% of women with breast cancer have a family member with this disease.

Having a personal history of breast cancer

A woman with cancer in one breast has a higher risk of developing a new cancer in the other breast or in another part of the same breast. (This is different from a recurrence or return of the first cancer.) Although this risk is low overall, it's even higher for younger women with breast cancer.

Your race and ethnicity

Overall, white women are slightly more likely to develop breast cancer than African-American women. But in women under age 45, breast cancer is more common in African-American women. African-American women are also more likely to die from breast cancer at any age. Asian, Hispanic, and Native American women have a lower risk of developing and dying from breast cancer.

Having dense breast tissue

Breasts are made up of fatty tissue, fibrous tissue, and glandular tissue. Someone is said to have dense breasts (on a mammogram) when they have more glandular and fibrous tissue and less fatty tissue. Women with dense breasts on mammogram have a risk of breast cancer that is about 1.5 to 2 times that of women with average breast density. Unfortunately, dense breast tissue can also make it harder to see cancers on mammograms.

A number of factors can affect breast density, such as age, menopausal status, the use of certain drugs (including menopausal hormone therapy), pregnancy, and genetics.

Certain benign breast conditions

Women diagnosed with certain benign (non-cancer) breast conditions may have a higher risk of breast cancer. Some of these conditions are more closely linked to breast cancer risk than others. Doctors often divide benign breast conditions into 3 groups, depending on how they affect this risk.

Non-proliferative lesions: These conditions don’t seem to affect breast cancer risk, or if they do, the increase in risk is very small. They include:

Fibrosis and/or simple cysts (sometimes called fibrocystic changes or disease)
Mild hyperplasia
Adenosis (non-sclerosing)
Phyllodes tumor (benign)
A single papilloma
Fat necrosis
Duct ectasia
Periductal fibrosis
Squamous and apocrine metaplasia
Epithelial-related calcifications
Other tumors (lipoma, hamartoma, hemangioma, neurofibroma, adenomyoepithelioma)

Mastitis (infection of the breast) is not a tumor and does not increase the risk of breast cancer.

Proliferative lesions without atypia (cell abnormalities): In these conditions there’s excessive growth of cells in the ducts or lobules of the breast, but the cells don't look very abnormal. These conditions seem to raise a woman’s risk of breast cancer slightly. They include:

Usual ductal hyperplasia (without atypia)
Fibroadenoma
Sclerosing adenosis
Several papillomas (called papillomatosis)
Radial scar

Proliferative lesions with atypia: In these conditions, the cells in the ducts or lobules of the breast tissue grow excessively, and some of them no longer look normal. These types of lesions include:

Atypical ductal hyperplasia (ADH)
Atypical lobular hyperplasia (ALH)

Breast cancer risk is about 4 to 5 times higher than normal in women with these changes. If a woman also has a family history of breast cancer and either hyperplasia or atypical hyperplasia, she has an even higher risk of breast cancer.

Lobular carcinoma in situ (LCIS)

In LCIS, cells that look like cancer cells are growing in the lobules of the milk-producing glands of the breast, but they are not growing through the wall of the lobules. LCIS is also called lobular neoplasia. It’s sometimes grouped with ductal carcinoma in situ (DCIS) as a non-invasive breast cancer, but it differs from DCIS in that it doesn’t seem to become invasive cancer if it isn’t treated.

Women with LCIS have a much higher risk of developing cancer in either breast.

Starting menstruation (periods) early

Women who have had more menstrual cycles because they started menstruating early (especially before age 12) have a slightly higher risk of breast cancer. The increase in risk may be due to a longer lifetime exposure to the hormones estrogen and progesterone.

Going through menopause after age 55

Women who have had more menstrual cycles because they went through menopause later (after age 55) have a slightly higher risk of breast cancer. The increase in risk may be because they have a longer lifetime exposure to the hormones estrogen and progesterone.

Having radiation to your chest

Women who were treated with radiation therapy to the chest for another cancer (such as Hodgkin disease or non-Hodgkin lymphoma) when they were younger have a significantly higher risk for breast cancer. This varies with the patient’s age when they got radiation. The risk is highest if you had radiation as a teen or young adult, when your breasts were still developing. Radiation treatment after age 40 does not seem to increase breast cancer risk.

Exposure to diethylstilbestrol (DES)

From the 1940s through the early 1970s some pregnant women were given an estrogen-like drug called DES because it was thought to lower their chances of losing the baby (miscarriage). These women have a slightly increased risk of developing breast cancer. Women whose mothers took DES during pregnancy may also have a slightly higher risk of breast cancer.