The goal of screening for breast cancer is to find breast cancer at early, treatable stages. Ways to screen for breast cancer include breast self-examination (women feel for lumps in their own breasts), clinical breast examination (doctors or nurses examine women's breasts for lumps), and mammography. Mammography is an x-ray of the breast that often shows breast tumors before they are large enough to feel. Experts do not all agree about whether mammography decreases breast cancer death rates. The disagreement is strongest for mammography in 40- to 49-year-old women.