What Is Fibroglandular Density?

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"Fibroglandular density" is a term used to describe how much of the breast tissue is dense or fatty. People with dense breasts have more fibrous and glandular tissue and less fatty tissue. This makes it more difficult for mammograms to catch breast cancer and can raise the risk of developing breast cancer.

This article will discuss types of breast tissue, define fibroglandular density, and its risk factors. It will also cover screenings used to identify fibroglandular density.

breast tissue

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Breast Tissue Types

The breast is made up of three different types of tissues, including:

  • Fibrous tissue: A supportive or connective tissue called ligaments. It stretches from the chest wall to the skin to hold the breast tissue.
  • Glandular tissue: Includes the breast ducts and lobes.
  • Fatty tissue: Also known as adipose tissue, it is largely what gives the breast its shape and fills in the areas between the glandular and fibrous tissue.

What Is Fibroglandular Density?

Fibroglandular density refers to breasts that have more fibrous and glandular tissue and less fatty tissue. This is also called dense breast tissue. After a mammogram, breast tissue is rated based on its density or fibroglandular ratio. The scale is as follows:

  • Almost entirely fatty breasts: 10% of women
  • Few areas of dense tissue: 40% of women
  • Evenly dense throughout: 40% of women
  • Extremely dense: 10% of women

If someone falls into the areas of entirely fatty breasts or a few areas of dense tissue, they have low fibroglandular density.

Those who have evenly dense tissue throughout or extremely dense tissue have high fibroglandular density. This means that fibroglandular densities are very common, with 50% of women in that category.

There are two important reasons for people to know if they have high fibroglandular density. These include:

  • More difficult breast cancer detection via mammogram: This is called masking. Fibroglandular densities and breast cancer both show up as white areas on mammograms, making it hard for healthcare providers to tell the difference.
  • Increased risk of breast cancer: There is a slightly increased risk of breast cancer for those with high fibroglandular density.

Risk Factors for Fibroglandular Densities

The amount of fibroglandular density someone has changes over time. Certain factors can put someone at a greater risk of having high fibroglandular densities, including:

Screenings for Fibroglandular Density

People with fibroglandular densities will be screened differently for breast cancer than other women. Therefore, it's important to know if someone has this type of breast tissue. A healthcare provider may use one of the following tools to screen someone for fibroglandular density:


Mammograms are X-ray pictures of the breast. They are used as the first-line screening for breast cancer and can identify if someone has dense breast tissue.

When someone has been identified as having fibroglandular densities or dense breast tissue, a healthcare provider may recommend further screening tools.


If you have dense breast tissue and are at an average risk for breast cancer, your healthcare provider may order a breast ultrasound.

Ultrasound uses sound waves to create an image of the breast. An ultrasound can identify abnormal breast tissue that a mammogram cannot detect.


An MRI uses magnets and radio waves to produce a detailed image. It can detect breast cancer in people with high fibroglandular density that a mammogram may miss.

The downside to MRIs is that they are more likely to produce false-positive results (detecting disease is present when it in fact is not). This can lead to additional unnecessary testing.


A breast biopsy is a procedure in which a small piece of breast tissue is removed and tested for cancer cells. The procedure may be used to detect a lump in the breast, to investigate problems seen on a mammogram, or to evaluate nipple problems.

These three types of breast biopsies can be performed:

  • Fine needle aspiration (FNA) biopsy: A thin needle is inserted into the area to remove a small amount of tissue for testing.
  • Core needle biopsy: A large needle is inserted into the area and cores out pieces of tissue.
  • Open biopsy: A surgical opening is made into the skin, and the necessary tissue is removed.


"Fibroglandular density" is a term used to describe how much of the breast tissue is dense or fatty. Mammograms can identify the density of the tissue.

If you have high fibroglandular density, you will need additional screenings to ensure the tissue is healthy and noncancerous. Having high fibroglandular density is normal but requires additional healthcare attention.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Memorial Sloan Kettering Cancer Center. Anatomy of the breast.

  2. National Cancer Institute. Dense breasts: answers to commonly asked questions.

  3. Centers for Disease Control and Prevention. Breast cancer.

  4. Centers for Disease Control and Prevention. What is a mammogram?

  5. MD Anderson. Dense breast tissue: what it is, and what to do if you have it.

  6. Johns Hopkins Medicine. Breast magnetic resonance imaging (MRI).

  7. Johns Hopkins Medicine. Breast biopsy.

By Patty Weasler, RN, BSN
Patty is a registered nurse with over a decade of experience in pediatric critical care. Her passion is writing health and wellness content that anyone can understand and use.