What Is a Mammogram?

What to expect when undergoing this test

Mammograms are an important tool both the screening and in the diagnosis of breast cancer. The test involves placing your breast between two plates and using X-ray imaging to look for any suspicious findings. A mammogram alone cannot be used to diagnose breast cancer but can aid in the diagnosis by classifying normal or suspicious findings in detail. Mammograms can sometimes detect breast cancers in the earliest stages before any symptoms are present but can miss some cancers as well, especially in younger women who have dense breast tissue.

what to expect during a mammogram
Illustration by Cindy Chung, Verywell

Purpose of Test

A mammogram may be ordered as a screening test (screening mammogram) to look for any evidence of breast cancer in women who do not have any symptoms.

Different organizations, including the American Cancer Society, the U.S. Preventive Services Task Force, and the American College of Obstetricians and Gynecologists have somewhat different breast cancer screening guidelines.

These recommendations are intended for women at average risk only. Those at increased risk may require earlier or more frequent mammograms or other screening tests such as magnetic resonance imaging (MRI).

A mammogram may also be done as a diagnostic test (diagnostic mammogram) for those who have any signs or symptoms of breast cancer, such as:

  • A breast lump or lump in the armpit (axillary mass)
  • Thickening or swelling of a breast or part of a breast
  • Dimpling of the breast skin
  • A change in the size or shape of the breast
  • A sense of heaviness in one breast
  • Nipple retraction (pulling in of a nipple)
  • Nipple discharge
  • Breast pain
  • Redness, scaling, a rash, or irritation of the breast or nipples (possible symptoms of inflammatory breast cancer or Paget's disease of the breast)
  • Itchy breasts

It's important to note that a mammogram may be recommended for men as well as women and that men can develop breast cancer also (though male breast cancer is much less common than breast cancer in women).

Limitations

A mammogram has limitations in returning accurate results. Despite being highly valuable, mammograms can vary in their sensitively (the ability to correctly render a positive result) and specificity (the ability to correctly render a negative result). The sensitivity and specificity can be influenced by numerous factors, occasionally leading to incorrect, or false, diagnoses.

False Negatives

A mammogram cannot always detect the presence of breast cancer when one is present. This is referred to as a "false-negative" result. According to a 2011 study in the American Journal of Roentgenology, false-negative diagnoses in women 50 to 59 occur at a rate of 14.4 cases for every 1,000 mammograms.

For women who have dense breasts, especially younger women, the rates may even be higher. Roughly 20 percent of breast cancers are not found on a screening mammogram when women have dense breasts. It's important to note that the term "dense breasts" is made based on the appearance of breasts on mammogram images and not by the size or feel.

Women must be informed if they have dense breasts and may consider the option of additional screening, such as breast ultrasound or fast breast MRI (abbreviated MRI).

In early studies, fast breast MRI has been found to be more likely to detect breast cancer (especially more aggressive breast cancers) with fewer false positives than the combination of mammography and ultrasound. In fact, some studies suggest that fast MRI may be comparable to conventional MRI (the screening method of choice for women who are high risk), despite taking only around 10 minutes and having a cost similar to mammography.

Breast cancers such as inflammatory breast cancer and Paget's disease of the breast are less likely to be seen on a screening mammogram. In addition, most women who have inflammatory breast cancer also have dense breasts, which further reduces the chance of spotting these cancers.

False Positives

Mammograms may also raise unwarranted concern over harmless breast changes, particularly with regards to benign breast lesions that can mimic breast cancer. These can lead to "false-positive" diagnoses along with more invasive testing and unnecessary treatment.

If you have a mammogram every year for 10 years, your chance of having a false-positive result at some point may be as high as 50 percent.

False-positive results are more common in younger women who have dense breasts, for those who have had previous surgery on their breast (such as a breast biopsy), for those who are using hormonal therapy, and for those who have risk factors for breast cancer.

Having a baseline mammogram available to compare with has been found to significantly reduce the chance of having a false-positive result. Unfortunately, a 2019 study found that almost two-thirds of women were aware of this and the importance of having a baseline test.

For women who have breast implants, images may not be as accurate without special views, as X-rays don't travel well through either saline or silicone. With special views (two for each breast) however, the accuracy is greatly improved. Overall, while the presence of implants has been found to reduce the detection of breast cancers on mammography, this is not associated with an increased risk of death in women who have them.

It is important to remember that a mammogram cannot diagnose breast cancer but can only reveal suspicious findings. A breast biopsy would be needed to make a definitive diagnosis.

Similar Tests

You may hear a distinction between conventional mammography and digital mammography, although digital mammography is most commonly used in the United States. The difference between the two is that conventional mammography is stored on film, whereas digital mammography is stored digitally.

Digital mammograms have the advantage of being able to be moved or magnified during readings and can be sent electronically. They are also more accurate in women with dense breasts and involve less radiation.

That said, digital mammography is usually more expensive than conventional mammography, and in some areas of the world, only conventional mammography may be available.

There are other forms of mammography that are now available or being evaluated in studies. Digital breast tomosynthesis (DBT), better known as 3D mammography, is similar to a computed tomography (CT) scan and uses multiple X-ray slices to create a 3-dimensional image of the breast. It involves slightly more radiation than digital mammography, and it's not known yet if there are any significant advantages of this technology. Optical mammography is also being evaluated.

Tests that have been evaluated as potential alternatives (or adjuncts) to mammography include:

  • Elastography: Elastography is a test that looks at the elasticity of the breast; it relies on the fact that many breast tumors have very low elasticity. It's not certain what role this test may play in the future, but it is currently used to determine if a biopsy is needed on a mass that is found, rather than as a screening test.
  • Thermography: Breast thermography evaluates the temperature of the skin over the breast and has been touted as a radiation-free method of looking for breast cancer. That said, there is currently no evidence that thermography is effective as a screening or diagnostic tool for breast cancer, and the test is not a substitute for mammography.

Complementary Tests

A number of different tests may be ordered along with a mammogram. If you find a lump, or if there is suspicion of a lump on a mammogram, a breast ultrasound may also be done. A breast ultrasound can help differentiate a cystic mass (breast cyst) from a solid mass.

Women who have an increased risk of developing breast cancer or women who have dense breasts may benefit from additional screenings, such as combining a breast MRI with mammography.

Risks and Contraindications

Mammograms expose women to a small amount of radiation, the amount of which rarely causes illness.

According to a 2016 study in the Annals of Internal Medicine, an estimated 125 of every 100,000 women who undergo an annual mammogram will develop radiation-induced breast cancer, of whom 16 (or 0.00016 percent) will die.

(By comparison, among the same group of women, 968 breast cancer deaths could be avoided as a result of the mammograms.)

The risk of radiation from mammograms is expected to be higher in those who receive higher doses of radiation and in women who have larger breasts, as they require additional radiation to accurately view all breast tissue.

For women who have breast implants, there is a small risk that an implant could rupture, and it's important to let the technician know you have implants before the procedure.

Before The Test

Before you have your mammogram, your doctor will ask you about any risk factors you have, as well as any symptoms of breast cancer.

Timing

Though the mammogram itself usually takes around 10 to 15 minutes to complete, plan on spending at least an hour at your appointment to check in and afford your radiologist time to review your images.

In general, a diagnostic mammogram often takes longer than a screening mammogram, as special views are frequently done to evaluate an abnormal area.

Location

There are many places where a mammogram can be conducted, including outpatient clinics, hospitals, and even mobile mammography units.

What to Wear

You will be asked to change into a gown before your mammogram. Since you will only need to remove clothing from above your waist, wearing a two-piece outfit can make this process faster and easier.

Personal Care Products

You will be asked to refrain from wearing deodorant on the day of your mammogram and should avoid using any creams or lotions on your breasts or armpits. Many of these products contain metallic particles (such as aluminum) that can interfere with the images obtained (particles may look like calcifications).

If you accidentally apply deodorant or lotion before your test, you will need to thoroughly wash your breasts and underarms before the test can begin.

Food and Drink

There are no restrictions on eating or drinking prior to a mammogram.

Cost and Health Insurance

Most health insurance companies cover screening mammograms, as well as mammograms that are done to evaluate symptoms. The average cost for a mammogram is around $100, but can vary by location and whether any special views are ordered.

For those who do not have insurance, there are a number of state and local programs that provide free or low-cost mammograms, and some employers also offer discounted mammograms. The National Breast and Cervical Cancer Early Detection Program, a program of the Centers for Disease Control and Prevention (CDC), also offers free or low-cost mammograms to low-income women.

If you are unable to find free or low-cost mammograms in your area, you may receive a discount if you let the clinic know that you do not have insurance.

What to Bring

If you had previous mammograms at another facility, you may be asked to bring your films to your appointment. Radiologists usually want an actual copy of the scan (most departments can burn a CD of your scan that you can take with you) rather than a written report.

Bringing your previous mammograms with you can provide your radiologist with points of reference for comparison, reducing the chance of a false-positive result.

As with any medical professional, radiologists are sometimes backed up due to emergencies. Bringing a book or magazine to read can help if you are forced to wait before the test.

Reducing Pain

Some women, especially those who have larger breasts, can find mammograms uncomfortable. There are a number of things you do ahead of time to make your mammogram less painful, such as:

  • Scheduling your mammogram 10 days after your period (Hormone levels fluctuate during the menstrual cycle, and your breasts are likely to be the least tender and swollen at this point.)
  • Using an anti-inflammatory medication such as Advil (ibuprofen) or Aleve (naproxen) one hour prior to the test
  • Avoiding caffeine during the week prior to your mammogram
  • Applying lidocaine gel or a lidocaine patch to your breasts 30 minutes to an hour before the test

During the Test

When you are ready for your test, a radiology technician will take you back into the mammogram suite. You may or may not see the radiologist who will review your images.

Pre-Test

Many clinics will have you complete a questionnaire before you have your mammogram. These forms usually ask about any risk factors you have for breast cancer, any symptoms you are having, and any previous history of abnormal mammograms, breast biopsies, or breast surgery.

You may also have markers placed on your breast. These are used for a number of different reasons, such as to mark nipples, moles, scars, and any lumps or areas of pain you have noticed.

You can ask the radiologist to provide you a comfort pad, if available, which cushions the breast while the images are being taken.

Throughout the Test

The test is usually performed while you are standing. The machine has handles you can grasp to help you remain still while the images are taken. For those who are unable to stand, sitting mammography may also be done.

When the test begins, your technician will help you place your breast between two plates. These plates are then compressed, squeezing your breast as the images are taken. Compression allows more tissue to be seen with less radiation, helps reduce blurring along the edges of the film, and allows X-rays to pass through the tissue more easily.

If you experience any discomfort, let the technician know. In some cases, your breast can be repositioned without compromising the image. Even so, each image usually takes only a minute or less to complete.

In a standard screening mammogram, two mammogram views are taken on each breast; one craniocaudal (a view of your breasts from above) and the other mediolateral-oblique (a view of your breasts from the center outwards). The mediolateral-oblique view captures more breast tissue and allows better visualization of the upper chest and armpit.

Additional views, such as spot compression, cleavage view, and others may be done if needed to get an accurate image of your breasts. If you have breast implants, you may need special implant displacement views done. Even when these are necessary, the test rarely takes more than 10 minutes to 15 minutes.

Post-Test

When your mammogram is completed, you may be asked to wait until the radiologist reviews your images. In some clinics, the radiologist may talk with you about your test and describe any findings. More commonly, however, a report will be sent to your primary care physician who will notify you of your results.

After the Test

There are no special steps you need to take after having a mammogram, though this is a good time to make sure you book your next test, as recommended.

The discomfort of breast compression often improves rapidly when the test is done, but some women continue to feel aching in their breasts for a day or two after the test. If you do feel uncomfortable, wearing a comfortable sports bra or camisole, rather than a tightly fitted underwire bra, may provide some relief.

You can also apply a heating pad or soak in a warm bath. Using anti-inflammatory medications such as Advil (ibuprofen) may provide some relief as well.

Interpreting Results

After your mammogram, a radiologist will review your images and compare these with any previous mammograms you have had. The time it takes until your results are available can vary, and, with some clinics, it may take up to a month before a written report is sent to you.

Your mammogram report will include the following information:

  • Patient information
  • Medical history
  • Procedures (such as previous biopsies)
  • Findings
  • Impression (referred to as a BIRADS classification)
  • Recommendation for further tests, if needed

It is extremely important to contact your doctor if you have not received your results. Don't assume that all is fine if you haven't heard anything.

Findings

The findings section may simply say that your test was normal, negative, or benign. But if your radiologist sees anything that is suspicious or suggestive of malignancy, the report will describe the size of the finding, the location, and the shape or outline of the abnormal region.

There are a number of terms that may be used to describe findings, including:

  • Clustered breast calcifications or microcalcifications (calcifications appear as white "spots" on a mammogram, and their significance can vary)
  • A spiculated mass (a lump that has spikey borders like a starfish)
  • An asymmetrical density of breast tissue
  • Skin thickening
  • Retraction (areas of skin or nipple pulling inward)
  • Focal distortion (something is pressing on tissue)

In all cases, the report may also include a description of the density of your breast tissue.

BIRADS Classification

Your mammogram report will include a Breast Imaging Reporting and Data System number—the BIRADS classification—which is a number used to indicate your radiologist’s overall impression of your mammogram. This scale was developed to help standardize mammograms done across the country and at different institutions.

The scale for BIRADS goes from zero to five, with higher numbers indicating a greater possibility of breast cancer:

  • 0: The mammogram report is incomplete and an impression cannot be given until further views are done, other tests (such as an ultrasound) are performed, or the mammogram is compared with previous films.
  • 1: Negative
  • 2: Benign findings, such as benign calcifications or a benign fibroadenoma
  • 3: Probably benign, with a 98 percent chance that it is not cancer (this usually means you will need earlier follow-up, such as a mammogram in six months)
  • 4: Suspicious abnormality; a biopsy is often indicated. This can be broken down into 4A, 4B, and 4C, with 4A meaning a lower chance that it is cancer, and 4C indicating a higher chance of the disease.
  • 5: Highly suggestive of malignancy; a biopsy should be done. Radiologists give a score of 5 when they estimate the chance that the findings mean cancer is 95 percent or higher.

A BIRADS score of 6, meaning cancer, can only be made with a breast biopsy.

Follow-Up

Your radiologist may make some recommendations based on your mammogram results. In some cases, no other studies may be needed. But if so, they may include:

  • Three-month or six-month follow-up imaging
  • Spot views
  • Magnification
  • Diagnostic mammogram
  • Breast ultrasound for lumps and masses, as this test can often distinguish between solid masses and breast cysts; you may get this the same day as your mammogram
  • Breast MRI: There are several differences between a mammogram and an MRI in the evaluation of breast tissue, and an MRI may be more accurate for those who have a family history, other risk factors, or dense breasts.
  • Breast biopsy to conclusively diagnose or rule out breast cancer

If your mammogram is normal, it's important to continue to follow breast screening guidelines. Keep in mind that screening guidelines are for women who are asymptomatic. If you have any symptoms of breast cancer, further testing or sooner follow-up may be needed.

If any abnormalities are found, or if the mammogram is difficult to interpret, talk to your doctor. The radiologist will be able to review your images, but your primary physician can also look at your risk factors, findings on physical exam, and your medical and family history, to help guide you as to your next steps.

A Word From Verywell

Scheduling and then waiting for the results of your mammogram can cause anxiety, especially if further tests or a biopsy are recommended. Keep in mind that even when a biopsy is recommended based on findings on a screening mammogram, 60 percent to 70 percent of these biopsies turn out to be benign (not cancerous).

While mammograms can sometimes detect cancer in the earliest of stages before symptoms appear, it's worth repeating that mammograms sometimes miss breast cancers and that a negative test does not guarantee that you don't have breast cancer. Fortunately, tests such as breast MRI are now available for those who are at a high risk of developing the disease, or who have dense breasts that reduce that accuracy of mammograms.

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