Mammograms are x-ray images of the breast that can reveal early signs of breast cancer.

There are two techniques for creating a mammogram. Film-screen mammography creates a photographic film, while digital mammography creates digital images.

Both methods use the same procedure for taking the image. The person having the mammogram will place their breast between two clear plates, which will squeeze it between them to hold it in place. This flattens the breast for a better image and stops the image from blurring.

The machine takes a picture of the breast from two angles. A specialist then checks the mammogram for anything unusual that could be a sign of cancer.

The test takes about 20 minutes. Some people may feel slight pain or discomfort.

How does a normal mammogram look?

The image of the breast is known as a mammogram. The background of the image will be black, and the breast will show up in grays and whites.

Tissue that is denser, including connective tissue and glands, shows up white.

Some people have more dense tissue in their breasts. This can make it harder to detect abnormalities on a mammogram as a tumor is made up of dense tissue and will also appear white.

The breasts tend to become less dense with age. Less dense tissue, such as fat, shows up gray on a mammogram.

A standard mammogram will usually be mostly gray, with some white areas showing healthy dense tissue. More white on the image does not always indicate a health problem.

Everyone's breasts are different, so no two mammogram images will be the same. Healthy mammograms can still vary in appearance.

A medical professional who checks imaging tests, such as X-rays or MRI scans, is called a radiologist. They will look carefully at the mammogram to interpret the results.

What does breast cancer look like on a mammogram?

Any area that does not look like normal tissue is a possible cause for concern. The radiologist will look for areas of white, high-density tissue and note its size, shape, and edges.

A lump or tumor will show up as a focused white area on a mammogram. Tumors can be cancerous or benign.

If a tumor is benign, it is not a health risk and is unlikely to grow or change shape. Most tumors found in the breasts are noncancerous.

Small white specks are usually harmless. The radiologist will check their shape and pattern, as they can sometimes be a sign of cancer.

Other abnormalities

As well as dense breast tissue and possible tumors, a radiologist will look for anything unusual on a mammogram.

Other abnormalities include:

• Cysts, which are small fluid-filled sacs. Most are simple cysts, which have a thin wall and are not cancerous. If a doctor cannot classify a cyst as a simple cyst, they may do further tests to ensure that it is not cancerous.
• Calcifications, which are deposits of calcium. Larger deposits of calcium are called macrocalcifications and they usually occur as a result of aging. Smaller deposits are called microcalcifications. Depending on the appearance of the microcalcifications, a doctor may test them for possible signs of cancer.
• Fibroadenomas, which are benign tumors in the breast. They are round and may feel like a marble. People in their 20s and 30s are more likely to have a fibroadenoma, but they can occur at any age.
• Scar tissue, which often appears white on a mammogram. It is best to make a doctor aware of any scarring on the breasts beforehand.

A mass may refer to a tumor, cyst, or fibroadenoma, whether it is cancerous or not.

A mammogram can also give a person information about their breast density. People with dense breasts have a slightly higher risk of breast cancer. Dense breasts can make it more difficult to find abnormalities on a mammogram.

Mammograms are still possible if a person has had breast cancer surgery or implants. However, it may be necessary to take more images of each breast, and it might take longer to check the images.

A radiologist will often compare a mammogram against previous images. This can help them to spot any changes and decide whether an unusual area could be a sign of cancer.

When to see a doctor

People should examine their breasts regularly and see a doctor if they have any concerns.

By being aware of how their breasts usually look and feel, they are more likely to notice any changes.

The American Cancer Society (ACS) has published recommendations on the number of mammograms that women should have at each age:

• women aged 40 to 44 should have the choice to begin annual mammograms
• women aged 45 to 54 should have a mammogram every year
• women aged 55 and older can switch to having a mammogram every 2 years

If a woman has a family history of breast cancer, doctors may offer them a mammogram before the age of 40.

A mammogram to detect breast cancer in its early stages is called screening. If someone has already noted a sign or symptom of breast cancer, they may have a mammogram to confirm it. This is called a diagnostic mammogram.

Understanding the results

There is a standard system for reporting the results of a mammogram, which is called the Breast Imaging-Reporting and Data System, or BI-RADS.

BI-RADS uses categories with the numbers 0 to 6. This is to make sure that doctors across the United States are using the same terms.

Category meaning: 0, An unclear result with a need for more tests or comparison with previous mammograms; 1, No abnormalities; 2, No sign of cancer but some abnormalities present, such as benign calcifications; 3, Some abnormalities that are very likely to be benign, but need following up; 4, Abnormalities that could be cancerous, possibly requiring a biopsy; 5, Abnormalities very likely to be cancerous, requiring a biopsy; 6, Cancer is present, requiring mammograms to check progress.

A medical professional should explain the results clearly. They may recommend further tests to check anything that looks suspicious.

It is common to need further tests after a mammogram, as doctors will want to look more closely at any abnormalities on the images. A call-back does not necessarily mean that cancer is present.

Takeaway

Mammograms are currently the best method available for detecting breast cancer or checking to see how breast cancer is responding to treatment. However, mammograms are not perfect, and it can be difficult to see any abnormalities in people with dense breasts.

A mammogram will look different for every individual, and there is no standard normal or abnormal image.

Areas that appear white on a mammogram may need follow-up tests, but are not often the result of breast cancer.

—Claire Sissons