Causes & Risks

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At the Swedish Cancer Institute, we are experts in diagnosing and treating breast cancer. With leading specialists and the latest technology, we offer personalized care and medical expertise.

Some key risk factors and how SCI can help


Being born a woman is the greatest risk factor for breast cancer. About 1 in 8 women, or 12 percent, will develop breast cancer in their lifetime. While men can develop breast cancer, they make up about 1 percent of all cases in the US.


The risk of developing breast cancer increases with age. About 80 percent of all breast cancers occur in women over 50. The disease is uncommon in women under 35. African American women are at risk for developing breast cancer at younger ages than white women. For men, the average age for developing breast cancer is 68.

Family history without proven genetic mutation

A man or woman whose mother, sister or daughter has had breast cancer is at higher risk. The risk increases further if the family member's cancer was in both breasts or was diagnosed before menopause.

Genetic mutation

Five to 10 percent of all breast cancers are hereditary. If breast cancer runs in your family, a genetic counselor can assess your risk.

Age of menstruation

A woman who began her period before age 12 has an increased risk of breast cancer.

Having children

Having no children or a first child after age 30 raises a woman’s risk of breast cancer.

Atypical breast cells

Women who have been found to have atypical breast cells such as an overgrowth of cells in the ducts or lobules of the breast tissue are at greater risk of breast cancer.

Other risk factors

  • Hormone replacement therapy, or HRT – particularly combined estrogen and progestin taken for five years or longer
  • Women or men with a history of Hodgkin’s lymphoma treated with mantle radiation therapy
  • Men with radiation exposure or those with high levels of the hormone estrogen
  • Elevated body weight, alcohol consumption, low physical activity and smoking are under investigation as risk factors
  • Risks of hormone replacement in transgendered male-to-female individuals are under study

If you believe you are at risk for breast cancer, or have questions about your potential risk, the Swedish Cancer Institute has a High Risk Clinic to assess your concerns. To make an appointment to talk with an advanced nurse practitioner, call 206-215-6400.