Mammography

DEFINITION: Mammography is a radiographic procedure used to examine internal breast tissue for possible abnormalities. Mammograms are either screening or diagnostic and can be film-screen, 2D digital or 3D digital.

ALSO KNOWN AS: Breast X-ray

In a screening mammogram, X-ray images of the breast are recorded on X-ray film (conventional method) or electronically (digital method). The recommendation for screening mammograms has varied across health organizations. While the American Cancer Society advises women at average risk should have a screening mammogram done annually starting at the age of forty-five, the US Preventive Services Task Force changed its guidelines in 2024 to recommend women at average risk have a screening mammogram done every other year beginning at age forty instead of age fifty. Patients with a family history of breast cancer, however, should have their first mammogram before forty years of age and should continue to have them yearly. Also, regardless of age, patients who have been diagnosed as having breast cancer should have a mammogram yearly.

In a diagnostic mammogram, a series of X-ray images of the breast from various angles are recorded on X-ray film (conventional method) or electronically (digital method). Diagnostic mammograms are used to diagnose lumps that a woman feels during self-examination or a healthcare provider detects during a clinical breast examination if other unexpected symptoms—such as a change in breast shape or size, or occurrence of nipple discharge, breast pain, or thickening of breast skin—are present. During a diagnostic mammogram, more X-rays are taken than during a screening mammogram to get views from many angles. A diagnostic mammogram may be required if the patient has breast implants to be able to view breast tissue that can be hidden by the implant.

In a digital mammogram, X-ray images of the breast are recorded electronically and are stored on a computer. The images can then be manipulated via computer software for further evaluation. The average dose of radiation used is lower than that for film mammography. In terms of cancer detection, no differences between digital imaging and traditional film imaging have been found for the general population. Digital mammography is considered preferable, however, for those women who are under the age of fifty, have dense breasts, or are premenopausal or perimenopausal.

In addition, the National Cancer Institute (NCI) has supported research to develop new procedures for detecting breast tumors. Technologies that have been investigated have included magnetic resonance imaging (MRI), ultrasound elastography, and positron emission tomography (PET) as well as methods to detect genetic markers for breast cancer, which involve analysis of blood, urine, or fluid aspirated from the nipple. Contrast-Enhanced Mammography involves injecting a contrasting dye into the breast before the mammogram, making it easier to detect breast abnormalities. Artificial intelligence is also increasingly used to analyze mammography results and provide feedback that human eyes may miss. 

Cancers diagnosed: Breast cancer

Why performed: In the United States, aside from some skin cancers, the most frequently occurring cancer for women is breast cancer. Mammography allows for the screening and early detection of breast-tissue abnormalities. Statistics indicate mammography can result in detection of breast cancer one to two years before it can be detected by breast self-examination. Early detection of breast cancer improves the chances for successful treatment of this form of cancer.

Patient preparation: The patient should shower or bathe prior to the mammogram and should not use deodorant, body lotions, sunscreens, creams, powders, or perfume on the chest or underarms, as they may cause “artifacts” (false images) to appear on the X-ray image.

Steps of the procedure: Patients who have breast implants should mention that fact when making the mammogram appointment. Both the technologist who performs the mammogram and the radiologist who interprets the mammogram must have experience in working with implants.

Prior to undergoing mammography, the patient will be asked if they have undergone any type of breast surgery, as this may affect the way in which the X-ray films are interpreted. They will then be asked to remove all clothing and jewelry from the waist up. The patient will be given a short gown and asked to put it on so that it opens in the front.

The procedure begins with the radiologic technologist placing one of the breasts on a platform and lowering a plastic plate onto the breast until it is flattened as much as possible. This allows for the successful X-ray visualization of as much breast tissue as possible. The technologist then positions the X-ray machine, stands behind a protective barrier, and takes the image. A front-view X-ray (from the upper surface down) and a side-view X-ray of the breast will be taken. Next, the technologist repeats this procedure with the other breast. While the patient may feel uncomfortable when the breast is being flattened, this discomfort is short in duration.

After the procedure: The patient will be asked to wait while the X-ray films are developed and then viewed by a radiologist to make sure that none of the images need to be retaken. Once this has been confirmed, the patient will be allowed to redress and use deodorant.

The patient should ask how long it will take to get the results of the mammography and whether those results will be sent to the patient as well as to the doctor. They may also want to ask where the “films” will be stored so that they can be retrieved if the patient moves out of the area and needs to have future mammograms performed at another location. This is important because the new radiologist may use those earlier images as a reference to determine if there have been any changes in breast tissue over time.

Risks: Mammography uses low-dose radiation and is considered to be very safe. Patients who are pregnant or think they may be pregnant, however, should not have a mammogram. A pregnant person should not be exposed to X-rays because of the possible risk to the fetus.

The safety and reliability of mammograms are mandated by a federal law called the Mammography Quality Standards Act (MQSA). This law requires that all mammography facilities in the United States meet stringent quality standards, including those for the medical physicist, who tests the mammography equipment; the technologist, who takes the mammogram; and the radiologist, who interprets the mammogram. The facilities must also maintain certification by the Food and Drug Administration (FDA) and undergo an annual inspection.

Results: A normal result means that the X-ray films revealed no obvious signs of breast cancer. In certain instances, however, breast cancer may still be present. This false negative result is more common for those with denser breast tissue, as is typical for younger women. The denser the breast tissue, the more difficult it is to visualize abnormal spots on the X-ray image.

An abnormal result means that something has been identified that needs to be looked at more closely. The abnormality may be an unusual-looking area of breast tissue or a type of cyst or lump. Even the presence of a lump, however, does not necessarily indicate cancer. A lump can be either (noncancerous) or (cancerous). Therefore, additional testing such as a diagnostic mammogram, ultrasound, or biopsy may be required to determine if the abnormality is the result of breast cancer. The most common type of biopsy is known as a needle biopsy. This procedure consists of inserting a small-gauge needle into the area in question and removing a small tissue sample. That sample is then sent to a laboratory for determination if any cancerous cells are present. An abnormality that is interpreted as breast cancer when none is present is called a false positive result. Like the false negative result, it is more common for younger people. It is also more common for those who have a family history of breast cancer, have had a previous breast biopsy, or are taking estrogen.

The American College of Radiology (ACR) has established a system for uniform reporting of mammogram results called the Breast Imaging Reporting and Database System (BI-RADS) that consists of seven categories. Radiologists and physicians use it to help determine appropriate patient care.

Bibliography

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