A mammogram is an x-ray of the breasts that is read by a radiologist, or a doctor trained to examine x-ray photography. For the exam, the breast is pressed between 2 plates to flatten and spread the tissue. This may be uncomfortable, but it’s needed to get a good, clear picture. The pressure only lasts a few seconds. The entire mammogram procedure takes about 20 minutes. The mammogram is not a perfect diagnostic tool: 2 out of 3 women who get abnormal results do not actually have cancer, and it is possible that you detect a lump that is not detected by the screening. Talk to your doctor about whether you should have your results confirmed with a biopsy (in which a piece of breast tissue is taken out and examined), which is the only way to 100% confirm if you have breast cancer.