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Guideline: What is breast density and why does it matter?

New FDA guidelines for mammograms will go into effect by September 2024. Current FDA guidance requires hospitals and breast centers to give people information about their breast density with their mammogram results. By September 2024, mammogram providers will need to relay to patients who have dense breast that they should discuss the need for additional imaging. This article provides an overview of what breast density means and why it matters. (Posted 6/8/23)

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RELEVANCE

Most relevant for: People who have mammograms.

It may also be relevant for:

  • previvors
  • people with a genetic mutation linked to cancer risk
  • people with a family history of cancer
  • healthy people with average cancer risk

Relevance: Medium-High

Relevance rating details

GUIDELINE AT A GLANCE

What is this guideline about?

The now requires that breast density be included in a report.

Why is this guideline important?

Women with dense breasts have a higher chance of getting breast cancer. In addition, dense breast tissue makes it more difficult to find breast cancer on a mammogram.  It is the perfect storm. Breast density both increases your risk of having breast cancer and makes it harder to find cancer. However, having dense breasts is just one of several risk factors. Knowing about your breast density as well as other risk factors can help you and your doctor decide whether you should have additional screening that may include a breast or .  

What's in a mammogram report?

Mammogram reports have two scores.

  • A number score between 0 and 6 indicates the finding on your mammogram, such as nothing of concern, non-cancer findings or abnormalities.
  • A letter score of A to D indicates your breast density. A and B means your breasts are not dense.  C and D means you have dense breast tissue.  

What is breast density?

Breast density is a rating of how much breast tissue you have.  The only way to determine breast density currently is with a mammogram.  It appears as white areas on your mammogram.  The denser your breast tissue is the harder it is for doctors to spot cancer on a mammogram.

Breasts are made up of different types of tissue. Breasts with lots of fat appear black or dark on . Breasts with lots of breast tissue have more white areas on the mammogram. This makes it harder to find cancer because breast cancers also appear as white spots or areas on a mammogram. If you have more white breast tissue, it is harder to identify the white breast cancer because of the lack of contrast between the normal breast tissue and the cancer. In addition, people with dense breasts have an increased risk of breast cancer.

How is breast density reported?

Everyone's breasts are different. The amount of dense or fatty tissue varies from person to person.

Doctors use a standard system to report mammogram results. The BI-RADS (Breast Imaging and Reporting System) rates breast tissue for the potential presence of cancer and for density. BI-RADS uses letters A through D to separate breast density into four groups:

  • A   Fatty:  The tissue is not dense.
  • B   Scattered fibroglandular: The tissue is mostly fatty but has some dense areas.
  • C   Heterogeneously dense:  Areas of dense tissue are present. This may make it hard to see small tumors. This occurs in about 40% of people.
  • D   Extremely dense:  It is very difficult to see masses in the breast. This occurs  in about 10 percent of people.

People with a BI-RADS score of C or D have dense breasts.

infographic with the different types of breast density scores and what they mean

What do BI-RADS number scores mean?

A BI-RADS (Breast Imaging Reporting and Database System) number score is provided on every mammogram report to indicate whether mammogram findings are normal or abnormal. Not all abnormal findings are cancer.

  • Category 0: A score of 0 indicates an incomplete test. The images may have been difficult to read or interpret, and additional screening is required.
  • Category 1:  The radiologist saw nothing of concern.
  • Category 2: Nothing indicates cancer, but non-cancer findings, such as a cyst, were detected.
  • Category 3: Changes from your previous mammogram that are probably not cancer were identified. Your doctor may recommend additional imaging in 6 months or sooner.
  • Category 4: An abnormality that looks like cancer was found and your doctor will recommend a biopsy to determine whether it is benign or cancer.
  • Category 5:  An abnormality was detected and is likely cancer. Your doctor will recommend a biopsy.
  • Category 6:  This score is used only for people who have already been diagnosed with breast cancer.

What does the FDA’s update change?

The 2023 FDA update is a significant change for many hospitals and clinics and one that will benefit people who have mammograms. This change is the result of years of advocacy by healthcare professionals and people with dense breasts whose cancers went undetected by mammograms. Hospitals and clinics have until September 2024 to make these changes.

The update makes two changes:

  • Hospitals and clinics offering mammograms are required to provide people with information on the density of their breasts. Some hospitals and clinics already provide this information. If you are screened at a facility that already does, you may not see a change in the information you received in the past.
  • To improve mammogram accuracy, the FDA will work with hospitals and clinics to make sure that they provide and read mammograms correctly.