It is possible to develop breast cancer with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of developing breast cancer. If you have a number of risk factors, ask your health care provider what you can do to reduce your risk.

A risk factor is something that increases your likelihood of getting a disease or condition.

Breast cancer is found predominantly in women and is the most common form of cancer in North American women. However, men can develop breast cancer as well; it is estimated that approximately 180 men develop breast cancer each year in Canada.

Genetic Factors
Women who have a family history of breast cancer (mother, sister, or daughter) have a higher risk factor of developing breast cancer. However, a lack of family history does not protect you from developing breast cancer; approximately 90%-95% of women who develop breast cancer have no family history of this disease.

Additionally, having a mutation in the BRCA1 or BRCA2 breast cancer genes increases your risk.

Breast cancer can develop at any age in adulthood. However, it is quite rare in women under age 35. The chance of developing breast cancer increases with age, and three out of four cases occur in women over age 50. However, it is never safe to say that “you are too young to get breast cancer.”


The following medical conditions have been found to increase the risk of developing breast cancer:

  • Prior personal history of breast cancer, or other abnormalities in the breast tissue
  • Breasts that have a high proportion of lobular and ductal tissue instead of fatty tissue
  • Previous breast exposure to radiation therapy before age 30
  • Pregnancy after age 30, or no pregnancy at all
  • Overweight, particularly after menopause
  • Increased exposure to estrogen, which includes:
    • First menstrual period before age 13
    • Menopause after age 51
    • Use of estrogen replacement therapy
  • Exposure to large amounts of radiation (x-rays or cancer treatment), such as scoliosis treatment or treatment for Hodgkin’s disease
  • Previous biopsy results that indicate atypical hyperplasia, radial scar formation, or carcinoma in situ


Lifestyle factors that increase breast cancer risk include:

  • Drinking three or more alcoholic drinks daily
  • Sedentary lifestyle
  • Smoking


In the Canada, Caucasian, and African-Canadian women have the highest rates of breast cancer. The lowest rates occur among Korean, Native Canadian, and Vietnamese women.

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