Causes of Breast Cancer

Most women who develop breast cancer have no risk factors other than simply being a woman and getting older (especially being over 50). Talk to your doctor about your risk.

Other risk factors for breast cancer include:

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  having had breast cancer before
• family history of breast cancer (especially in a mother, sister or daughter diagnosed before menopause or if mutations on BRCA1 or BRCA2 genes are present)
• family history of ovarian cancer
  
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  an above-average exposure to the hormone estrogen, which your body naturally produces, perhaps because you:
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  have never given birth or gave birth for the first time after age 30
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  began menstruating at a young age
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  reached menopause later than average
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  have taken hormone replacement therapy (estrogen plus progestin)
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  dense breast tissue (as shown on a mammogram)
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  a history of breast biopsies showing certain breast changes, such as an increased number of abnormal cells that are not cancerous (atypical hyperplasia)
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    radiation treatment to the chest area (for example, to treat Hodgkin lymphoma), especially before age 30

Some factors slightly increase your risk of breast cancer. You may be at slightly higher risk if you:

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  are obese (especially after menopause)
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  drink alcohol
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  take birth control pills (the Pill)

Some women develop breast cancer without having any of these risk factors. Most women with breast cancer do not have a family history of the disease.

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