What role does breast density play in breast cancer screening?

Women's Health
Female nurse conducting a mammogram screening for a female patient.

There’s no question that regular mammograms are the best screening method to detect breast cancer. Ongoing research continues to shape the recommendations that your health care provider may give you about when and how often you should be screened for breast cancer, based on risk. Breast density is one factor that plays an important role in your breast cancer screenings.

Because breast density is a key element in breast health, in March 2023 the Food & Drug Administration (FDA) issued a new rule about it. Among other things, the regulations require mammogram facilities to inform each patient about their breast density.

Here’s what you need to know about breast density and why it matters when it comes to screening for breast cancer.

What is breast density?

There are three different kinds of tissue in your breasts.

  1. Fibrous tissue: Also called connective tissue, it supports the breast tissues to keep them in place.
  2. Glandular tissue: Made up of glands that produce milk and ducts (small tubes) that bring the milk from the glands to the nipple.
  3. Fatty tissue: Fat that fills the spaces between the fibrous and glandular tissues; gives breasts their shape and size.

Together, the first two types of tissue are called fibroglandular tissue.

Your breast density is assessed visually by comparing how much fibroglandular tissue you have compared to how much fatty tissue you have.

"The only way to determine your breast density is with a mammogram — you can’t tell just by your breast size or by feel," says Ida Teberian, MD, a radiologist at Main Line Health.

The more fibroglandular tissue you have compared to fatty tissue, the more dense your breasts are. This density can change as you age.

"Dense breasts are normal and common. In fact, almost half of all women 40 and older have dense breasts," says Dr. Teberian. "About 10% of women have breasts that are almost completely fatty tissue and about 10% have breasts that are extremely dense. Most women fall somewhere in between."

In general, you’re more likely to have dense breasts if you’re pregnant or breastfeeding, if you’re younger (premenopausal), if you’re using hormone replacement therapy (HRT) post-menopause and if you have a low body mass index (BMI).

Why does breast density matter?

Catching cancer as early as possible and starting treatment can lower your risk of dying from breast cancer, particularly if you’re between the ages of 40 and 74.

Screening mammograms can detect breast cancer early, even before you can feel any lumps or have any symptoms. As with any test, there are some limitations, one of which is related to greater breast density.

Dense breasts make cancer screening more difficult

Fibroglandular tissue shows up as white on a mammogram, while fatty tissue appears dark. Cancerous areas and tumors, unfortunately, also appear as white.

This means that the more dense your breasts are, the more difficult it can be to spot cancer. In fatty breasts, it’s much more likely that your radiologist (the person who interprets your mammogram) will notice a tumor. It’s important to keep in mind that radiologists are looking for many signs of possible cancer on mammograms, including changes from prior studies, architectural distortion and calcifications, all of which can be seen regardless of density.

Having dense breasts increases your risk of breast cancer

Completely separate from the fact that increased breast density makes it slightly more difficult to spot cancer early, having dense breasts is an independent risk factor for developing breast cancer.

Scientists aren’t sure why, but the more fibroglandular tissue you have, the higher your risk of developing cancer. At the very least, this is simply due to having more breast tissue and cells from which cancer can arise. There are many other factors at play that are less clear, but this is an active area of investigation.

What should you do if you have dense breasts?

Even though breast density can complicate mammograms and is, itself, a risk factor for breast cancer, there are numerous ways you and your health care provider can take charge of your breast health.

Additional testing

There are other screening tools like breast MRI that may give a clearer picture of your breasts. Your health care provider will be able to weigh your family history as well as your personal history and health to determine if additional testing is right for you.

Lower your other risk factors for breast cancer

Regardless of your breast density which is predetermined, there are other breast cancer risk factors that you can change.

Some important ways to lower your risk of breast cancer and take control of your breast health include:

  • Getting regular exercise: Physical activity lowers your risk of breast cancer.
  • Eating a healthy diet: Vegetables, fruits, whole grains and lean proteins are linked to lower cancer rates.
  • Keeping your body at a healthy weight: Obesity and weight gain as an adult lead to a higher risk of breast cancer.
  • Avoiding/limiting alcohol: Drinking alcohol raises your risk of breast cancer.

Most importantly, regular appointments with your health care provider and health screenings like mammograms are the best ways to be proactive about your breast health.

If you have dense breasts, guidelines recommend that you speak with your health care provider about what your breast density means for your individual breast cancer risk.

It’s never too early — or too late — to take steps toward better breast health. Being aware of how your breast density impacts important screening tools like mammograms can help you and your health care provider take steps to meet your individual health care needs.

Next steps:

Meet Ida Teberian, MD
Learn about breast cancer care at Main Line Health
The truth behind 4 common cancer myths