Dense Breast Tissue & Cancer Risk: What You Should Know

Sandra Brennan with a patient

Radiologist Sandra Brennan specializes in breast imaging and minimally invasive biopsies.

What are dense breasts and how common are they?

Having dense breasts is a risk factor for breast cancer. In many states, radiologists (doctors who specialize in imaging tests) must tell you if your screening mammogram shows you have dense breasts.

Breasts are made of both fibrous and glandular tissue, and fat. Breast density describes the amount of fibrous and glandular tissue compared with the amount of fat. There are different levels of dense breasts. Some are more common than others.

  • About 1 out of every 10 women have very dense breasts.
  • Around 4 out of every 10 women have heterogeneous density. That means their breasts are mostly dense, with some areas of fat.
  • Another 4 out of every 10 women have scattered density. That means some areas are dense, but most are not.
  • About 1 out of every 10 women have breasts that are mostly fat. They have no fibrous and glandular tissue, or very little.

Sandra Brennan, Director of Radiology at MSK Westchester provides more information below about breast density. She shares steps people with dense breasts can take to find cancer early. 

Does dense breast tissue raise your risk of breast cancer?

People with dense breasts have a higher risk of breast cancer. People with the highest density are 4 to 6 times more likely to get breast cancer than people with the least dense breasts. This is because glandular tissue is more likely to develop cancer. However, even people with breasts that are mostly fatty can get breast cancer.

Having dense breasts also makes it harder to see signs of cancer on a mammogram. The dense tissue looks white on the image, so it can hide lumps that are cancer. It’s harder to find cancer in dense breasts early, when it’s easier to treat.

To learn more about the risk factors for breast cancer, please see MSK’s breast cancer screening guidelines.

What causes dense breasts?

They’re mostly just part of the natural makeup of your body. Density is affected by age and hormones. Hormone replacement therapy will make breasts more dense. The drug tamoxifen (Nolvadex®) will make them less dense. Tamoxifen is an estrogen-receptor drug used to treat some types of breast cancer. Breasts can become less dense as you age, or stay the same. 

Is there anything you can do to reduce your breast density?

It’s not really something you can change. There are no foods or supplements that make a difference. Some people may have changes in the amount of fat in their breasts if they lose or gain weight. Women with a low body mass index tend to have dense breasts.

Mammograms & Other Types of Breast Exams
Learn about the different types of breast exams that can help detect breast cancer at its earliest stages, before symptoms develop.

What are MSK’s breast cancer screening recommendations for people with dense breasts?

If You’re at High Risk for Breast Cancer

  • Starting at age 20, have a breast exam by your healthcare provider every 6 months.
  • Have a mammogram or tomosynthesis every year. Start no later than 10 years before the youngest age that a close blood relative was diagnosed with cancer. Do not start earlier than age 25.
  • Have an MRI every year and alternate with a mammogram every 6 months.
  • If you had radiation treatment, have your MRI, and mammogram or tomosynthesis, at the same time or every 6 months. Screening should begin 8 years after radiation treatment.
  • If you had top surgery and were assigned female at birth, talk with your healthcare provider about screening. You probably have breast tissue.
  • If you’re having or had gender affirming hormone therapy, talk with your healthcare provider about screening.

Learn more about average and intermediate risk for breast cancer and MSK’s screening recommendations.

What breast cancer screening tests and services are available at MSK?

People with dense breasts should talk with their healthcare provider about getting screened with ultrasound as well as a mammogram. A breast ultrasound can find cancer in dense breasts better than a mammogram. You can learn more about breast cancer screening methods.

MSK uses 3D mammography, also known as tomosynthesis. This technology is better at finding tumors in dense breasts than traditional 2D mammograms. They take pictures with more details. Their 3D images are in layers, and taken from many different angles. In mammograms, dense tissue and lumps are the same color. The 3D mammogram technology makes it easier to see lumps that may be cancer.

MSK offers 3D mammography, screening breast ultrasounds, and breast MRIs. We offer contrast-enhanced mammograms, which uses iodinated contrast dye. This dye makes it easier to find new blood vessels that develop when cancers grow.

Everyone screened for breast cancer at MSK will get a 3D mammogram, in Manhattan or at our regional sites. We offer screening at the Evelyn H. Lauder Breast Center in Manhattan. MSK offers breast cancer treatment at locations in New York City, New Jersey, Westchester County, and on Long Island.

Breast cancer screening services are available at all MSK locations. Anyone who needs a screening mammogram can make an appointment at MSK. We welcome all MSK patients, our employees and their families, and the community.  We accept all prescriptions for screening mammography and breast ultrasounds.

If you need a breast biopsy, we offer nonsurgical procedures. These include percutaneous ultrasound-guided core biopsies, fine-needle aspirations, stereotactic breast biopsies, and MRI-guided biopsies. People who are having surgery at Memorial Hospital in Manhattan can have pre-surgical procedures at our regional locations. This includes radioactive seed localizations and sentinel node injections.