• Mammograms expose you to low-dose radiation. The dose is very low, though, and for most women the benefits of regular mammograms outweigh the risks posed by this amount of radiation.
• Mammograms aren't always accurate. The accuracy of the procedure depends in part on the technique used and the experience and skill of the radiologist. Other factors — such as your age and breast density — may result in false-negative or false-positive mammograms.
• Mammograms in younger women can be difficult to interpret. The breasts of younger women contain more glands and ligaments than do those of older women, resulting in dense breast tissue that can obscure signs of cancer. With age, breast tissue becomes fattier and has fewer glands, making it easier to interpret and detect changes on mammograms.
• Having a mammogram may lead to additional testing. Among women of all ages, about 10 percent of mammograms require additional testing, including additional imaging tests such as ultrasound, and a procedure (biopsy) to remove a sample of breast tissue for laboratory testing. However, most abnormal findings detected on mammograms aren't cancer. If you're told that your mammogram is abnormal, ask the radiologist to compare your current mammogram with any previous mammograms.
• Screening mammography can't detect all cancers. Some cancers detected by physical examination may not be seen on the mammogram. A cancer may be too small or may be in an area that is difficult to view by mammography, such as your armpit. Mammograms can miss 1 in 5 cancers in women.
• Not all of the tumors found by mammography can be cured. Certain types of cancers are aggressive, grow rapidly and spread early to other parts of your body.

During the test

At the testing facility, you're given a gown and asked to remove neck jewelry and clothing from the waist up. To make this easier, wear a two-piece outfit that day. For the procedure itself, you stand in front of an X-ray machine specially designed for mammography. The technician places one of your breasts on a platform and raises or lowers the platform to match your height. The technician helps you position your head, arms and torso to allow an unobstructed view of your breast. Your breast is gradually pressed against the platform by a clear plastic plate. Pressure is applied for a few seconds to spread out the breast tissue. The pressure isn't harmful, but you may find it uncomfortable or even painful. If you have too much discomfort, tell the technician. Your breast must be compressed to even out its thickness and permit the X-rays to penetrate the breast tissue. The pressure also holds your breast still to decrease blurring from movement and minimizes the dose of radiation needed. During the brief X-ray exposure, you'll be asked to stand still and hold your breath.
After the test

After images are made of both your breasts, you may be asked to wait while the technician checks the quality of the images. If the views are inadequate for technical reasons, you may have to repeat part of the test. The entire procedure usually takes less than 30 minutes. Afterward, you may dress and resume normal activity. In the United State, federal law requires mammogram facilities to send your results within 30 days, but you can usually expect to receive your results sooner. Ask the technician what you can expect.

Mammography produces mammograms — black-and-white images of your breast tissue. Most mammograms are digital images that appear on a computer screen. A radiologist interprets the images and sends a written report of the findings to your doctor. The radiologist looks for evidence of cancer or noncancerous (benign) conditions that may require further testing, follow-up or treatment. Possible findings include: Calcium deposits (calcifications) in ducts and other tissues Masses or lumps Distorted tissues Dense areas appearing in only one breast or one specific area on the mammogram New dense area that has appeared since your last mammogram Calcifications can be the result of cell secretions, cell debris, inflammation and trauma, among other causes. Tiny, irregular deposits called microcalcifications may be associated with cancer. Larger, coarser areas of calcification may be caused by aging or by a benign condition such as fibroadenoma, a common noncancerous tumor of the breast. Most breast calcifications are benign, but if calcifications appear worrisome, the radiologist might order additional diagnostic images with magnification. Dense areas indicate tissue that is more glandular than fatty, which can make calcifications and masses more difficult to identify or differentiate from normal glandular tissue. Dense areas can also represent cancer. Distorted areas suggest tumors that may have invaded neighboring tissues. If the radiologist notes areas of concern on your mammogram, further testing may include additional mammograms known as compression or magnification views, as well as ultrasound imaging or a procedure (biopsy) to remove a sample of breast tissue for laboratory testing. Some situations require the use of diagnostic magnetic resonance imaging (MRI) in areas where the current imaging with mammography or ultrasound is negative and it's not clear what's causing a breast change or abnormality. .