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
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.