A mammogram is an X-ray of your breasts. Mammograms can detect an abnormality as early as two years before it can be felt.
A radiologist will review your mammograms looking for densities and irregular breast tissue with finger-like extensions. Sometimes they also see a cluster of microcalcifications, which can be a sign of breast cancer.
The risk of harm from low level radiation used in mammograms is extremely small.
Sometimes abnormal breast changes are not detected by mammograms. Therefore, you should never ignore a lump just because it is not visible on a mammogram. Your mammograms constitute an irreplaceable part of your health history. Being able to compare earlier mammograms with new films helps your local health care provider evaluate areas that may have changed. If you move, take copies of your mammograms with you.