About risk factors: Although there are some women who are at higher risk, the fact is all women are at risk for breast cancer. That's why it is so important to follow the three-step plan for breast health. Early detection of problems provides the greatest possibility of successful treatment. Some people with one or more risk factors never develop a disease, such as cancer, while others develop cancer and have no known risk factors. Although certain factors MAY suggest or define a person's possible risks, they do not necessarily cause the disease. Different diseases, including cancers, have different risk-factor lists. When reading about risk factors for breast cancer, keep in mind that the word "risk" is used in different ways: Lifetime risk refers to the probability that a person, over the course of his or her lifetime, will be diagnosed or die from cancer. Over her lifetime, a woman in the United States has a 1 in 8 risk of developing breast cancer, and a 1 in 35 risk of dying from breast cancer. Relative risk is a measure of the strength of the relationship between risk factors and cancer. With respect to breast cancer, it compares the risk of developing breast cancer in women who have a certain trait or exposure to women who do not have the trait or exposure. About 20 percent to 30 percent of women with breast cancer have a family member with this disease. Source: National Cancer Institute

Any woman may develop breast cancer. However, the following risk factors may increase the likelihood of developing the disease.

Risk factors that cannot be changed:

• gender
  Breast cancer occurs nearly 100 times more often in women than in men.
• aging
  Two out of three women with invasive cancer are diagnosed after age 55.
• personal history of breast cancer
• previous breast irradiation
• family history and genetic factors
  Having a close relative, such as a mother or sister, with breast cancer increases the risk. This includes changes in certain genes such as BRCA1, BRCA2, and others.
  benign breast disease
• previous breast biopsy in which the tissue showed atypical hyperplasia
• menstrual periods that began early in life
• menopause that began later in life

The most frequently cited lifestyle-related risk factors:

• smoking
• not having children, or first child after age 30
• oral contraceptives
• obesity and a high-fat diet
• physical inactivity
• alcohol
• long-term, post-menopausal use of combined estrogen and progestin (HRT)
• weight gain and obesity after menopause

Environmental risk factors:

Exposure to pesticides, or other chemicals, is currently being examined as a possible risk factor.