A risk factor, by definition, is anything that increases a person's chances of getting a disease. Having one or more risk factors, however, does not guarantee that disease will develop. As the American Cancer Society explains, many women have multiple risk factors for breast cancer and never receive a breast cancer diagnosis, whereas many who do develop breast cancer have no risks whatsoever.
Being Female
Being a woman is the greatest risk for developing breast cancer even though breast cancer is a disease that strikes both genders. It is, however, 100 times more common in women than in men, primarily because the breast cells in women have greater exposure to the female hormones estrogen and progesterone, explains the American Cancer Society. These hormones are responsible for the growth of cancer cells in breast tissue.
Age
The risk of developing breast cancer increases as a woman becomes older. The Mayo Clinic states that women over the age of 60 have a greater risk compared to younger women. The American Cancer Society agrees, adding that approximately 2 out of 3 invasive cancers---cancers that spread beyond the breast tissue---occur in women 55 or older.
Personal History
A woman with a previous history of cancer is three to four times more likely to develop a new cancer in either the second breast or in another area of the breast in which cancer was first diagnosed. The American Cancer Society points out that this new diagnosis differs from a breast cancer recurrence, which is the return of the original cancer.
Family History
Women whose blood relatives have a history of or currently have breast cancer have a greater risk of developing breast cancer. Having one first-line relative---such as a mother, sister or daughter---with the disease doubles a woman's risk, whereas having two first-line relatives increases her risk fivefold, states the American Cancer Society.
BRCA1 and BRCA2 Genes
The most common causes of hereditary breast cancer are mutations in the BRCA1 and BRCA2 genes. Mutations are abnormal changes in otherwise healthy genes. When cells are healthy, these genes help prevent the growth of cancer cells; however, when either of these genes mutate, the risk of developing breast cancer is as high as 80 percent. The American Cancer Society notes that cancers from these mutations tend to occur in younger women and usually occur in both breasts.
Dense Breast Tissue
Women have two types of breast tissue: dense and fatty. Doctors can see abnormalities in fatty breast tissue more easily than they can see those in dense tissue. For this reason, women with a greater amount of dense breast tissue have a greater risk of developing breast cancer.
