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Causes of Breast Cancer

For some women with the BRCA1 gene mutation, the lifetime risk of breast cancer is as high as 80 percent.

While there's no known exact cause of breast cancer, it’s known that the disease occurs when some breast cells begin growing abnormally.

These cells divide more rapidly than healthy cells and then start to accumulate, forming a lump or mass.

These cancer cells can spread (metastasize) throughout the breast and into lymph nodes or to other parts of your body.

Most of the time, breast cancer begins with cells in the milk-producing ducts. But it can also begin in the glandular tissue called lobules, or in other cells within the breast.

Risk Factors for Breast Cancer

While some people who get breast cancer don't have any of the following risk factors, these traits increase your risk of developing breast cancer:

Being a woman
Older age
Personal history of breast cancer in one breast (increases your risk of getting it in the other breast)
Family history of breast cancer in close relatives such as your mother, sister, or daughter - especially if they developed the disease at a young age
Inherited genetic mutations, such as BRCA1 and BRCA2
Radiation exposure to your chest as a child or young adult
Starting your menstrual cycle before the age of 12
Beginning menopause at an older age
Giving birth for the first time after the age of 35
Never being pregnant
Taking hormone therapy that combines estrogen and progesterone
Drinking alcohol

Inherited Breast Cancer

The majority of breast cancers are not inherited. In fact, only 5 to 10 percent of breast cancers are linked to genetic mutations passed down through generations.

The most common gene mutations linked to breast cancer are BRCA1 and BRCA2. Both of these mutations also increase the risk of other cancers throughout a woman's lifetime, particularly ovarian cancer.

In normal cells, the BRCA1 and BRCA2 genes help prevent cancer by making proteins that keep the cells from growing abnormally. If these genes are mutated, the cancer-prevention response will not work properly.

For some women with the BRCA1 mutation, the lifetime risk of breast cancer is as high as 80 percent. On average, however, this risk is more like 55 to 65 percent.

For women with the BRCA2 mutation, the lifetime risk of breast cancer is around 45 percent.

Breast cancers linked to these mutations occur more often in younger women. Cancer affecting both breasts is also more common than in cases not linked to these mutations.

While the BRCA1 and BRCA2 mutations may affect anyone, they are more common in Jewish people of Eastern European origin than in other racial and ethnic groups in the United States.

Men can also carry these mutations, and if they do they are at increased risk for breast and other cancers, such as prostate cancer.
Genetic Testing

Genetic testing may be an option if you have a family history of breast cancer or other cancers.

Through a blood or saliva test, scientists can identify specific inherited mutations in BRCA or other genes.

Talk with your doctor about whether genetic testing is a good option for you. Your doctor can also recommend a genetic counselor who can discuss your testing options with you in detail.

Check with your insurance company to see if BRCA1 and BRCA2 mutation testing is covered under your plan.

Genetic counseling and testing for people at high risk is a covered preventive service under the Affordable Care Act (ACA).

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