American Cancer Society’s guidelines for early detection of breast cancer

Screening tests are used to find cancer before a person has any symptoms. 
Here are the American Cancer Society's recommendations to help guide you when you talk to your doctor about screening for breast cancer:
Women ages 40 to 44 should have the choice to start annual breast cancer screening with mammograms (x-rays of the breast) if they wish to do so.
Women ages 45 to 54 should get mammograms every year.
Women 55 and older should switch to mammograms every two years, or can continue yearly screening.
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Screening should continue as long as a woman is in good health and is expected to live 10 more years or longer.
All women should be familiar with the known benefits, limitations, and potential harms linked to breast cancer screening. 
Women should also know how their breasts normally look and feel and report any breast changes to a health care provider right away.
Some women – because of their family history, a genetic tendency, or certain other factors, should be screened with MRIs along with mammograms. The American Cancer Society urges anyone to talk with a health care provider about your risk for breast cancer, and the best screening plan for you.