What is breast density?

Breast density describes the kind of tissue that makes up a woman's breast:

  • Fatty tissue, which is easy to see through on a mammogram
  • Fibrous tissue, which is made up of fibers like nerves or muscles 
  • Glandular tissue, which is made up of glands like milk ducts 

Women with dense breasts have more fibrous and glandular tissue, which can make breast cancer hard to see on a mammogram. It is a common finding, especially among younger women.

How is a woman's breast density determined?

A radiologist assesses breast density from a patient's mammogram and reports it on a scale:

  • Almost entirely fatty: most of the tissue is made up of fat cells
  • Scattered areas of fibroglandular density: some tissue is fatty and some is either fibrous or glandular
  • Heterogeneously dense: more than half the tissue is fibrous or glandular
  • Extremely dense: most of the tissue is fibrous or glandular

Women with heterogeneously or extremely dense tissue are considered to have dense breasts. Forty to 50% of women in the US fall in these categories.

Why is it important to know if you have dense breasts?

Dense tissue can make breast cancer hard to see because both appear white on a mammogram. One of the reasons we use breast tomosynthesis is because it allows us to see though layers of dense tissue and pinpoint the size, shape and location of an abnormality.

What should women do if they have sensitive breasts?

Women should talk to their doctor about their risk of breast cancer and find out which screening tests are right for them. For some women with dense breasts, a physician may recommend additional tests such as a breast MRI or ultrasound. Women should also talk to their insurance company to find out if these tests are covered.



Levels of Breast Density

Our breast radiologists assess breast density from a patient's mammogram and reports it on a scale. We include breast density in our mammogram results.