Risk factors

Researchers have linked a number of factors with a higher risk of breast cancer. Yet most women who are diagnosed have none of them. What does that mean for you? It means you should be vigilant about getting mammograms regardless of whether you have known risk factors. And your vigilance should grow as you get older, since the risk of breast cancer rises with age and is greatest after age 60.

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Some risk factors for breast cancer, such as starting menstruation before age 12, obviously cannot be changed. For more on these, see below. For those risk factors you can change, such as keeping your weight down, see our section on prevention.

Risk factors include:

• Belonging to a family with a strong history of breast cancer; the more first-degree relatives--mother, sister, or daughter--who have had the disease, particularly before age 50, the greater your own chances of getting it. Your risk also increases if a male member of your family has been affected or you have relatives with both breast and ovarian cancer.
• Having an inherited mutation in the genes that normally help regulate cell growth: BRCA1 and BRCA2 gene mutations increase your lifetime risk to between 40 percent and 80 percent. Other genetic mutations have also been associated with breast cancer.
• Having previously had breast cancer, or having one of two conditions in which abnormal cells are found in the breast, including atypical ductal or lobular hyperplasia and lobular carcinoma in situ (LCIS).
• Beginning menstruation before age 12 or reaching menopause after age 55, both of which increase a woman's lifetime exposure to estrogen. More than five to 10 years of hormone replacement therapy (especially the estrogen-progesterone combination) after menopause also may put women at greater risk. Men who have had disease characterized by high levels of estrogen, including cirrhosis of the liver and Klinefelter's syndrome, a genetic condition, appear to be more likely to develop breast cancer.
• Having a first pregnancy after age 35.