What are dense breasts?
Dense breasts are made up of a higher amount of dense fibrous and glandular tissue compared to fat tissue. You can’t tell that you have dense breasts by the way your breasts look or feel, but a mammogram can show you if you have high or low breast density.
The three tissues in your breasts that make up your breast density include:
- Fibrous connective tissue: This tissue in the breast helps connect and hold other tissues together. It is a dense tissue and shows up white on your mammogram.
- Glandular tissue: Your milk ducts and glands in your breast are called glandular tissue. This type of tissue is also dense and appears white on your mammogram.
- Fatty tissue: Fatty tissue isn’t dense like connective or glandular tissue. It shows up as see-through on a mammogram, making it easier to see a lump or area of concern.
The four dense breast tissue categories include:
A: Almost entirely fatty. This means your breast is almost all fatty tissue, typical in about 10% of people.
B: Scattered fibroglandular density. Scattered areas of glandular and fibrous connective tissue are found throughout your breasts, but there is still a higher amount of fat tissue. This type is found in about 40% of people.
C: Heterogeneously dense. You have fibrous and glandular evenly throughout your whole breast, meaning your breasts are mostly dense. About 40% of people are in this category.
D: Extremely dense. You have a very high breast density, meaning most of your breast tissue is dense. Extremely dense breasts are found in about 10% of people.
Dense breast tissue categories
The amount of connective, glandular and fatty tissue in the breasts varies from person to person. And a wide range of breast density—from low to extremely dense—is normal. However, knowing that you have high breast density and understanding what it means for your care is helpful. That way, you can take steps to protect your breast health.
Doctors use four categories to describe whether you have dense breast tissue and the amount of breast density. These categories are based on how much tissue can be seen on your mammogram images. Dense breast tissue is very common, and as many as half of people who get a mammogram are told they have heterogeneously dense or extremely dense breasts.
What causes dense breast tissue?
How much dense breast tissue you have is affected by many factors, such as your age, weight and hormones, including synthetic hormones taken as part of care for breast cancer or menopause. In general, dense breasts are more common in younger and leaner people.
- Age: Breasts tend to be denser when you are younger. For example, people in their 40s are likelier to have dense breasts than those in their 70s.
- Body mass index (BMI): A lower body mass index makes you more likely to have less fatty tissue in your breasts and more dense breast tissue.
- Hormone replacement therapy (HRT): It’s more common for people taking hormone replacement therapy as a treatment for menopause to have higher breast density.
- Family history: The makeup of your breast tissue may run in families. You’re more likely to have dense breast tissue if others in your family also have high-density breasts.
Breast density after menopause
The changes in your hormone levels when you reach menopause—or the end of your menstrual cycle—cause many effects on your body. After menopause, the dense fibrous connective and glandular tissue in your breasts usually decreases. That means you’re more likely to have less dense breast tissue after menopause.
This decline in dense breast tissue happens in those who go through menopause naturally and in people who have their ovaries removed with surgery, which causes early menopause. When you use hormone replacement therapy (HRT) for menopause, it may slow down this process of decreasing breast density. As a result, people who take HRT are more likely to continue having dense breast tissue until they stop HRT.
Why is breast density important?
Breast density is important because high-density breasts makes it harder to see breast cancer and other conditions on a mammogram. This is because both breast cancer and dense breast tissue appear white on the images, making it difficult to distinguish between them. It’s also important because having dense breasts increases your risk of breast cancer.
Dense breasts on a mammogram
Because dense breasts can’t be felt or seen, you won’t know how dense your breast tissue is until you have a mammogram. Breast density shows up in a range on mammography images— from mostly see-through fatty tissue to very dense tissue that appears white.
To help you be informed about your breast health and density, the Food and Drug Administration (FDA) requires every imaging provider in the country, including our imaging centers, to give you information about your breast density after a mammogram.
With this important information, you can talk with your doctor about what your breast density category means for your health. If you have heterogeneously dense or extremely dense breasts, ask about additional imaging tests or care to help check for signs of breast cancer and give you peace of mind.
Screenings for fibroglandular density
A mammogram is the most recommended screening for all breast types, including those with fibroglandular density. For most people with an average risk and breast density, this is the only routine screening needed to check for signs of breast cancer, starting at age 40.
If you have a higher risk of breast cancer or your mammogram images show high breast density, your healthcare provider will talk with you about other screening options that are used along with a mammogram. Each type of screening has its benefits and risks. But additional tests can give your care team more information about your breast health so you can feel confident in your next steps.
Ultrasound
You might also have a breast ultrasound when dense breast tissue is found on a mammogram. This imaging test uses sound waves to create images, and it sometimes detects spots or signs of breast cancer that can’t be seen on a mammogram image.
MRI
A breast MRI is another test sometimes used in those with very dense breasts to screen for signs of breast cancer. It’s more sensitive than a mammogram and uses a computer, magnets and radio waves to create detailed breast images.
Mammography
If you have dense breasts, you should still have an annual screening mammogram. Choosing an imaging center that offers tomosynthesis, also called 3D mammography, can be helpful for those with high breast density. This type of mammography provides detailed images of your breast in thin layers.