Scattered fibroglandular tissue refers to the density and composition of your breasts. A woman with scattered fibroglandular breast tissue has breasts made up mostly of nondense, fatty tissue with some areas of dense tissue.

Breast tissue density is detected during a screening mammogram. A physical examination isn’t able to accurately determine your breast tissue density. Only an imaging test can do that.

In this article, we explore what it means to have dense breast tissue, along with the different categories of breast density, recommended cancer screening tests, and more.

Breasts contain different types of tissue. These include:

  • fibrous (or connective) tissue, which holds the different structures of the breast in place
  • glandular tissues, which are the tissues that produce breast milk
  • fatty tissue, which gives breasts their shape and size

Breast density refers to the amounts of these different tissue types that are visible on a mammogram. Breasts that are described as dense have more fibrous and glandular (fibroglandular) tissue than fatty tissue.

When you have scattered fibroglandular breast tissue, it means that your breasts still contain mostly fatty tissue, but a few areas of fibroglandular tissue are visible on your mammogram. About 40 percent of women have this type of breast tissue.

As the amount of fibroglandular tissue increases, there’s a decrease in fatty tissue. When a large amount of fibroglandular tissue is seen in a mammogram, you’re said to have dense breasts. About 50 percent of women have dense breasts.

The only accurate way to measure and diagnose breast density is with a mammogram.

As of 2019, the federal government requires that all mammography reports explain how dense a woman’s breast tissues are. The idea behind this requirement is to help women understand if they have a higher chance of mammograms missing cancer because of their breast tissue density, and then prompt them to talk with their doctors to determine how to manage this.

Dense breast tissue can complicate a breast cancer diagnosis. Finding tumors among the dense breast tissue can be difficult. Additionally, women with dense breast tissue tend to have an increased chance of breast cancer compared with women whose breast tissue is less dense.

During a mammogram, your radiologist will look for unusual lesions or spots that may indicate cancer. They will also examine your breast tissue and identify different characteristics of the tissue, including density.

The different types of breast tissue vary in appearance on a mammogram:

  • Fibrous tissue. Fibrous tissue appears white on mammograms. This type of tissue is difficult to see through and tumors, which also appear white on a mammogram, can hide behind it.
  • Glandular tissue. Glandular tissue includes structures like lobules and milk ducts. It also appears white on a mammogram and, like fibrous tissue, is difficult to see through. This means lesions or questionable spots may be difficult to detect.
  • Fatty tissue. Fatty tissue is easy for a mammogram to penetrate, so it will appear see-through or dark on the scan.

A mammogram will also help your doctor determine what category of density you have. We’ll discuss the different categories of breast density in the next section.

Radiologists use something called the Breast Imaging Reporting and Data System (BI-RADS) to categorize breast tissue density. This system was developed by the American College of Radiology.

BI-RADS groups breast density into four different categories. In order of least to most dense, these breast tissue categories are:

  1. Fatty breast tissue. Fatty breast tissue is when your breasts are composed almost entirely of nondense fatty tissue. About 10 percent of women have fatty breast tissue.
  2. Scattered fibroglandular breast tissue. This category includes breasts that have scattered areas of dense tissue, but have a higher ratio of nondense fat. About 40 percent of women have scattered fibroglandular breast tissue.
  3. Heterogeneously dense breast tissue. For this category, the breast includes some nondense fat, but much of the tissue in the breast is fibroglandular. About 40 percent of women have heterogeneously dense breast tissue.
  4. Extremely dense breast tissue. When most of the tissue in your breast is dense, the density is considered “extreme.” About 10 percent of women have extremely dense breast tissue.

When you’re told that you have dense breasts, it means that your breasts fall into one of the last two categories — heterogeneously dense breast tissue or extremely dense breast tissue.

Breast density and breast cancer

In addition to making breast cancer harder to detect using a mammogram, dense breasts are an independent risk factor for breast cancer. The chance of breast cancer tends to increase with breast density.

Right now, doctors aren’t exactly sure how breast density itself contributes to breast cancer. It’s possible that, because breast cancer typically forms in glandular tissue, the fact that dense breasts have more of this tissue type plays an important role.

A 2014 research review found that, compared to women with scattered fibroglandular breast tissue, the risk of breast cancer in women with heterogeneously dense breast tissue increased modestly by a factor of 1.2 to 1.5. In women with extremely dense breast tissue, the risk doubled, increasing by a 2.1 to 2.3 factor.

The increasing risk of breast cancer with increasing breast density can be illustrated by a 2021 study that assessed breast density and the risk of breast cancer in 193,787 women ages 65 and older. The 5-year occurrence of breast cancer cases was found to be:

Fatty breast tissueScattered fibroglandular breast tissueHeterogeneously or extremely dense breast tissue
Ages 65 to 74: 11.3 per 1,000 womenAges 65 to 74: 17.2 per 1,000 womenAges 65 to 74: 23.7 per 1,000 women
Ages 75 and older: 13.5 per 1,000 womenAges 75 and older: 18.4 per 1,000 womenAges 75 and older: 22.5 per 1,000 women

Breast density can also change over time. One 2020 study of 74,249 women ages 35 and over found that the risk of breast cancer decreased as breast density decreased. Having persistently dense breasts was associated with an increased risk of breast cancer.

It’s currently unclear why some women have one type of breast density over another, and how a woman develops the type of breast tissue she has. Doctors don’t believe women can do anything yet to actively alter their breast density.

Genetics may play a role in breast density. That means that if other close relatives, such as a mother or sister, have dense breasts, you may as well.

Hormones may also be important. Exposure to hormones, fluctuating hormone levels, and medications that contain hormones, such as hormone replacement therapy, may change a woman’s breast tissue density ratio.

For example, breast tissue becomes less dense during menopause. This coincides with a decrease in estrogen levels.

Some risk factors tend to increase a woman’s chance of dense tissue:

  • Age. Breast tissue tends to become less dense with age.
  • Medication. Women taking certain hormonal medications may increase their chance of dense tissue. This can be true for women who use hormone replacement therapy to ease the symptoms of menopause.
  • Menopause status. Women who are premenopausal often have greater breast density than women who are postmenopausal.
  • Family history. Breast density appears to run in families, so you may be genetically predisposed to having dense breasts. Ask your mother and other women in your family to share their mammogram results.
  • Body mass index (BMI). Women that have a lower BMI are more likely to have more dense breasts.

Scattered fibroglandular breast tissue is a finding on a screening mammogram. It’s not a health condition and doesn’t need to be treated.

Instead, doctors and medical researchers are focused on encouraging women to find out what type of breast density they have and what to do with that information.

For example, women who have dense breast tissue, either heterogeneously dense or extremely dense, in addition to other risk factors for breast cancer may need additional breast cancer screening tests. A simple mammogram alone may not be enough.

These additional screening tests may include:

  • 3D mammogram. While your radiologist is performing a regular mammogram, they may also perform a 3D mammogram, or breast tomosynthesis. This imaging test takes pictures of your breast from several angles. A computer combines them to form a 3D image of your breast.
  • Breast ultrasound. A breast ultrasound uses high frequency sound waves to create images of breast tissue. This type of imaging test is also used to investigate any areas of concern in the breast.
  • Breast MRI. An MRI is an imaging test that uses magnets and radio waves, not radiation, to see into your tissue. A breast MRI is recommended for women with dense breasts who also have an increased chance of breast cancer based on other factors, such as genetic mutations.

If your mammogram results show that you have dense breasts, be sure to discuss this finding with your doctor. Based off of your overall chance of breast cancer, they may recommend additional screening tests.

It’s important to have a conversation with your doctor about when to start regular breast cancer screenings.

Regular screening allows doctors to see changes over time, which can help them identify any areas of concern. It may also provide an opportunity for doctors to catch cancer early before it’s had a chance to advance.

The exact recommendations for breast cancer screening can vary by organization. We’ll examine the recommendations from three different organizations below.

American Cancer Society recommendations

The current American Cancer Society (ACS) recommendations for women with an average chance of breast cancer are:

  • Women should have the option of beginning annual screening mammograms between the ages of 40 and 44.
  • If annual screening mammograms aren’t started within this timeframe, then women should start receiving them starting at 45 years old.
  • Women ages 55 and older have the option of continuing to receive annual screening mammograms or switching to having screening mammograms every other year.

The ACS issues slightly different recommendations for women who are considered to have a high chance of breast cancer. In this case, women should receive both a mammogram and a breast MRI each year, starting at 30 years old.

They do note that there’s currently not enough evidence to support yearly breast MRIs for women at an increased chance of breast cancer due to dense breast tissue. As such, it’s important to have an open discussion with your doctor about your overall chance of the condition and when you should begin screening.

U.S. Preventative Services Task Force recommendations

The current U.S. Preventative Services Task Force (USPSTF) breast cancer screening recommendations are:

  • Women between the ages of 40 and 49 may choose to begin receiving screening mammograms every other year.
  • Women between the ages of 50 and 74 should have a screening mammogram every other year.
  • There’s currently insufficient evidence to assess the benefit of screening mammograms in women ages 75 or older.

They also mention that there’s currently not enough evidence to evaluate additional screening tests like breast ultrasound or breast MRI in women with dense breasts that have an otherwise normal mammogram result.

As of writing, the USPSTF breast cancer screening recommendations are undergoing an update. This means that newer recommendations may be issued in the future based off of more recent research.

American College of Obstetricians and Gynecologists recommendations

The American College of Obstetricians and Gynecologists (ACOG) currently recommend the following for women with an average chance of breast cancer:

  • Women at an average chance of breast cancer can choose to begin receiving screening mammograms beginning at 40 years old and no earlier.
  • Women should start having screening mammograms no later than 50 years old.
  • Women with an average chance of breast cancer should continue to receive screening mammograms until at least 75 years old.
  • The frequency of screening mammograms, either once a year or once every other year, should be determined based off of an open, informed discussion with your doctor.

The ACOG has also issued a statement for women with dense breasts. Currently, they don’t recommend additional screening tests in women with dense breasts who have no symptoms of breast cancer or have no additional risk factors.

What to discuss with your doctor

If you don’t know your breast tissue density, ask your doctor about it at your next appointment or before your next mammogram. After the mammogram, use these questions to help spark the conversation:

  • What type of breast tissue do I have?
  • Do I have dense breast tissue?
  • How does my breast tissue affect my mammogram and breast cancer screening?
  • Should I have additional screenings beyond the mammogram?
  • Is my chance of breast cancer higher because of my breast tissue type?
  • Am I taking any medications that might impact the percentage of dense tissue?

The more you know about your risk factors, the more proactive you can be about taking care of your body. By far, the best way to approach breast cancer is to find it early and begin treatment right away. Mammograms and other imaging tests can help you do that.

Scattered fibroglandular breast tissue is a finding on a mammogram. This type of tissue contains mostly fatty tissue with scattered areas of fibroglandular tissue. It’s common, affecting about 40 percent of women.

Generally speaking, women with scattered fibroglandular breast tissue are at a lower chance of breast cancer than women with dense breasts. Having dense breast tissue makes tumors harder to see on mammograms and is also an independent risk factor for breast cancer.

Regular breast cancer screenings can help to detect breast cancer early before it’s had the chance to grow and spread further. It’s important to have a conversation with your doctor about your overall chance of breast cancer and when you should start having regular screenings.