Breast Cancer Risk Factors

Most women who develop breast cancer have no identifiable risk factors other than their gender. The condition is 100 times more common in women. The growth of breast cancer tumors is often affected by the presence of estrogen and progesterone. The following risk factors result from exposure to these hormones:

  • Age (over age 50)
  • First pregnancy after age 30
  • Long-term synthetic hormone replacement therapy (HRT)
  • Menstruation before age 12
  • Menopause after age 50
  • Nulliparity (never gave birth)

Other risk factors include the following:

  • Alcohol use (Women who have 2 to 5 drinks daily have about 1.5 times the risk of women who do not consume alcohol.)
  • Family history of the disease (mother or sister with premenopausal breast cancer)
  • Genetic link
  • History of breast biopsy or radiation to the chest
  • Obesity
  • Personal history of the disease - women with a history of breast cancer are 3 to 4 times more likely to have a recurrence
  • Race (slightly more common in Caucasians)
  • Sedentary lifestyle

Recent studies have shown that breast cancer may be more aggressive (i.e., more likely to spread or recur) in women who are overweight or obese.

Approximately 5 percent of breast cancer cases have a genetic link that results from an inherited mutation in genes identified as BRCA1 and BRCA2. Patients who inherit an altered BRCA1 or BRCA2 gene have an increased risk for developing premenopausal breast cancer and are more likely to have family members with the condition. In August 2014, a study showed that women with a mutation in a gene called PALB2 have a one in three chance of developing breast cancer by the age of 70. Patients concerned about the genetic risk for breast cancer should speak to their health care practitioner about genetic testing.

Studies have shown that higher breast density increases the risk for breast cancer. Breast density is a term used term used to describe the composition of breast tissue (e.g., glandular tissue, connective tissue, fat tissue). Dense breast tissue appears white in mammograms.

Breast density, which is not related to breast size, is affected by several factors, including heredity, age, and race. The amount of dense breast tissue usually decreases after menopause. Women who continue to have high breast density following menopause are at increased risk for breast cancer.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 14 Aug 1999

Last Modified: 03 Sep 2015