Risk Factors

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:

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

Source: The Canadian Cancer Society at www.cancer.ca

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