Mammography is good at finding breast cancer, especially in women ages 50 and older.
Overall, the sensitivity of mammography is about 84 percent . This means mammography correctly identifies about 84 percent of women who truly have breast cancer. Sensitivity is higher in women over 50 than in younger women .
Learn more about sensitivity.
One downside of missing so few cancers is false positive results. These occur when a mammogram finds something that looks like cancer, but turns out to be benign (not cancer).
The more mammograms a woman has, the more likely she will have a false positive result that will require follow-up tests. The chance of having a false positive result after 10 yearly mammograms is about 50 to 60 percent [21-23].
The chance of a false positive result is higher among younger women and women with dense breasts . (Most women younger than 50 have dense breasts so there is overlap among these groups.)
Getting a false positive result can cause short-term fear and worry . However, these feelings and do not tend to have lasting effects . Remember, most women called back for a false positive result do not have breast cancer.
Some women take menopausal hormone therapy (MHT) to relieve menopausal symptoms. The use of MHT increases breast cancer risk (learn more) . So, the U.S. Food and Drug Administration (FDA) recommends women use only the lowest dose that eases symptoms for the shortest time needed .
Learn more about menopausal hormone therapy and breast cancer risk.
Studies are looking at how MHT affects the accuracy of mammograms. There are two main types of MHT used today: estrogen plus progestin and estrogen alone (learn more).
Results from the Women's Health Initiative showed that women who took estrogen plus progestin (but not women who took estrogen alone) had breast cancers found at more advanced stages than breast cancers found in women who did not take MHT [28-29]. Women who took either type of MHT had higher breast density and more abnormal mammograms (not explained by the higher breast density) that needed follow-up testing [28-32].
Exactly how, and if, these results may affect future breast cancer screening guidelines is unclear.
To get accurate mammogram findings, you need a high quality image and a good reading of that image. The training and experience of the radiologist who reads the mammogram may improve his/her ability to interpret the image. Radiologists who read a lot of mammograms each year are generally better able to interpret the images than radiologists who do not read them routinely [33-35].
Although a high-volume mammography center may help you feel assured your mammogram will be read correctly, a lower-volume center may be just as good at reading mammograms . Most lower-volume, certified mammography centers provide good quality screening. To find a certified mammography center in your area, visit the FDA website (www.fda.gov).
Although mammography is the most effective screening tool for breast cancer used today, it is not perfect. Mammography misses about 16 percent of breast cancers . Depending on certain factors (such as breast density) mammography may miss nearly 30 percent of breast cancers [8,37].
Combining mammography with clinical breast exam may improve its ability to find cancer. One study showed mammography plus clinical breast exam found about four percent more cancers than mammography alone . This improvement was even greater among women with dense breast tissue .
Other imaging tests in combination with mammography are under study for use in routine breast cancer screening.
Learn more about clinical breast exam.
Learn more about other imaging tests and emerging areas in early detection.
Learn more about breast density.