What is a mammogram? How does it work?

Breast cancer is common in the US and worldwide, but with earlier detection and improved treatment options, survival rates have improved. 

The most important tool when it comes to fighting breast cancer is identifying it in its earliest stages and regular mammograms are crucial for this. But it can be daunting to head to your healthcare provider regularly for this test. 

We’ve covered everything you need to know about how mammograms work, what you can expect during the exam, and what steps you can take to reduce your chances of developing breast cancer. 

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A mammogram is an X-ray of the breast. Simply put, your breast is wedged between two plastic or glass plates, and an X-ray scan is taken to look for any growths or tumors in the tissue. They’re a useful tool because they can often detect breast cancer in its early stages before any symptoms develop. 

Breast cancer treatment is most likely to be successful when the cancer is caught in its early stages. As a result, women who get regular mammograms are less likely to require intensive treatment or chemotherapy. They’re also more likely to recover from breast cancer. In fact, getting regular mammograms can reduce the average person’s risk of dying from breast cancer by 40% (Monticciolo, 2021).

Keep in mind, though, that mammograms are not used to diagnose cancer. They used to look for breast abnormalities that might be a sign of cancer and they can help your healthcare provider decide if more testing is needed. 

Typically, your provider will look for things like calcifications (calcium deposits) in the breast tissues or ducts, masses or lumps, dense areas, cysts, or any other changes since your last mammogram if you’ve had one previously.

If they find something abnormal, they may ask you to undergo a biopsy, which is when a needle is used to collect a sample of tissue for further testing.

Sometimes mammograms can be done in a healthcare provider’s office, but not all spaces are equipped with the machinery used for mammography. Commonly, your provider will refer you to an imaging center where the scan will be performed by a technician. 

The results can then be sent back to your provider for analysis.

After you’ve checked in for your appointment, you’ll be taken to a private room. You’ll be asked to undress from the waist up and may be given a gown to wear. You’ll also be asked to remove any necklaces you might be wearing.

Now, you’re officially ready for the mammogram. Here’s how the X-ray process works:

• You’ll stand in front of the X-ray machine while the technician places one of your breasts onto a plastic or glass plate. They’ll adjust the platform to your height, and show you how to position your arms and torso.

• Another plastic or glass plate will descend from above and push down on your breast, making it flatter and holding it in place. This may be uncomfortable but it shouldn’t last long. By flattening the breast, it’s easier for the technician to get a clear picture. 

• They will likely ask you to hold your breath and hold still and then they will take a picture.

• The technician will reposition your breast to take an X-ray from the side view.

• The same process is repeated with the other breast.

Before finishing, the technician will check to make sure all the X-ray images were clearly captured. If one is off or a bit blurry, they’ll repeat the X-ray for that breast. If everything looks clear, the scans will be sent for analysis.

A radiologist will review your mammogram to look for early signs of breast cancer. They’ll summarize their findings in a report and send it to your healthcare provider, who should contact you with results. Be in touch with your provider regarding time frames and when you can expect results.

There are two main types of mammograms: screening and diagnostic (Magny, 2020).

• Screening mammograms: This type look for signs of breast cancer. This routine annual mammogram is recommended for women ages 40 and up without signs of breast cancer. 

• Diagnostic mammograms: These are used when there’s a change on your screening mammogram or if you experience other symptoms (new lump, pain, nipple thickening or discharge, skin change). Diagnostic mammography may also be used as a screening tool for women who have had breast cancer in the past.

Typically, mammograms produce a two-dimensional black and white image of the breast. However, 3D mammograms (called breast tomosynthesis) are a more recent option. Instead of pressing the breast twice, it’s only pressed once. Multiple images are taken as the machine scans over the breast before being compiled together into a 3D view. 

The potential benefits of 3D mammography are still being explored. However, research suggests that they may be able to detect more breast cancers and may reduce the need for follow-up testing. These may also be a better option for people with dense breasts (Rose, 2013; Svahn, 2015).

We’ll be straight with you: mammograms are not comfortable and can feel awkward or even painful. The good news is that they’re over quickly––each X-ray lasts only seconds. 

How a mammogram feels varies from woman to woman. It also depends on factors like the size of your breasts, or if you’re on your period and your breasts feel more sensitive.

Tips to make mammograms more comfortable

It is possible to make mammograms bearable. Try these tips:

• If you menstruate, schedule a mammogram after you’ve had your period. In the week prior to your period (as well as during), your breasts are more sensitive and the mammogram may feel more painful.

• For your appointment, wear a top with a skirt, pants, or shorts. You can keep your bottoms on during the mammogram, but if you wear a dress you’ll need to fully undress, which might be more uncomfortable for some. 

• Avoid using deodorant, lotion, and perfume near your arms or breasts as these can show up on X-ray images and require that you to repeat the scan.

• Take an over-the-counter pain medication (like ibuprofen) before your appointment.

From start to finish, the full scan typically takes less than 30 minutes. Each individual X-ray only takes seconds.

As for your results, you should hear something within a few weeks or sooner. By law, the FDA requires that a radiologist review the mammogram and share a report with your healthcare provider within 30 days (FDA, n.d.).

Women and transgender men who have not undergone bilateral mastectomy should receive regular mammograms starting at age 40 (Bazzi, 2015; Monticciolo, 2021).

Previously, health experts recommended women start getting annual mammograms at age 45. However, an increasing number of agencies––including the American College of Radiology, Society of Breast Imaging, and National Comprehensive Cancer Network––now recommend starting earlier. You should continue getting annual mammograms until at least age 75, and sometimes beyond (Oeffinger, 2015; Helvie, 2018). Consult with your healthcare provider to decide how often you should be checked.

Mammogram results can be normal or abnormal. If you have a normal mammogram, you can do monthly self-breast exams and report to your healthcare provider if you find anything abnormal.

If your mammogram results are abnormal, it doesn’t necessarily mean you have cancer. However, you will likely need to undergo another mammogram and testing to help your healthcare provider diagnose whether you do have breast cancer and if a biopsy is required (Magny, 2020).

Keep in mind that false positives (that is, tests reporting abnormalities that are not actually cancer) are more common in younger women, especially before age 50. That’s a big part of why healthcare experts encourage waiting until your forties to get tested regularly. 

False-negative results (that is, results that say you don’t have an abnormality when you actually do) are much less common. But these, too, are more common among younger people than older people since breast tissue is denser when you’re younger, making it more difficult to identify abnormalities (Nelson, 2016; Seely, 2018).

Yes. Screening mammograms are considered preventive. They are covered for women 40 and older every one or two years by Medicare and insurance under the Affordable Care Act.

Yes. The X-ray scan used for mammograms does expose your breasts to a small amount of radiation, but the benefits far outweigh the minor risks. 

It’s also worth noting that mammograms use a lower dose of radiation than a standard X-ray, which is why the machine uses plates. By flattening the breast, more tissue can be seen in the X-ray, minimizing radiation exposure. 

If you are pregnant or breastfeeding, let your technician know. Mammograms are safe during pregnancy due to the low amount of radiation, but the procedure may be modified to make it more comfortable (diFlorio-Alexander, 2018).

Mammograms are an important tool in the early detection of breast cancer. If you have any questions about mammography or notice any changes in your breasts, talk to a health professional.

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Current version

January 24, 2022

Written by

Amelia Willson

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.