The U.S. Preventive Services Task Force recommends mammograms every other year, while the American Cancer Society endorses annual scans. Kari Lehr/Image Zoo/Corbis hide caption

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Catharine Becker of Fullerton, Calif., was diagnosed with stage 3 breast cancer at 43 despite having a clean mammogram. The mother of three didn't know she had dense breast tissue until after she was diagnosed. Heidi de Marco/Kaiser Health News hide caption

itoggle caption Heidi de Marco/Kaiser Health News

Some researchers recommend starting mammogram screening at age 40, while others say age 50. Some doctors think screening should be based on a woman's overall risk for breast cancer, not just her age. Hero Images/Corbis hide caption

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Mammograms are a key screening tool for breast cancer. But critics say they're not good enough. Salih Dastan/iStockphoto hide caption

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A woman is positioned for a traditional mammogram at Tufts Medical Center in Boston. Bizuayehu Tesfaye/AP hide caption

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Mammography detects cancer, but debate rages over when and how often women should get screened. iStockphoto.com hide caption

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