What is Breast Density? 

Breast density is a way of describing the types of breast tissue that are seen on a mammogram. Breast density is not determined by how your breasts feel. The only way to find out the density of your breasts is through a mammogram. Your breasts are considered dense if you have a lot of fibrous or glandular (glan-juh-ler) tissue but not much fat. 

  • Glandular tissue is made up of the milk ducts and glands.

  • Fibrous tissue supports the breast.

  • Fatty tissue fills in the spaces between the other tissues. It gives the breast its size. 

What are the Four Levels of Breast Density? 

 

A. Almost all fatty:

  • Breast tissue is mostly made up of fat (1 out of 10 women)

B. Scattered areas of fibroglandular (fi-bro-glan-juh-ler) density: 

  • There are a few areas of fibrous and glandular tissue in the breast (4 out of 10 women)

 

 

 

 

C. Heterogeneously (het-er-uh-jee-nee-uhs-lee)

  • There are more areas of fibrous and glandular tissue throughout the breast (4 out of 10 women)

D. Extremely dense

  • Mostly fibrous and glandular tissue (1 out of 10 women)

 

 

 

What causes more dense breasts? 

Throughout your life, breast density can change. From year to year, your breasts may be either more or less dense. Things that affect breast density are: 

  • Age – usually, the younger the person the more dense the breast tissue

  • Genetic factors – family history

  • Use of hormones

  • Pregnancy or breastfeeding

  • Weight gain or loss 

Do I have dense breasts? 

Your mammography result letter will let you know if you have dense breasts (heterogeneously dense or extremely dense). Dense breasts are common and normal in many women. 

What should I do if I have dense breasts?

Breast tissue can be either dense or not dense. Dense tissue makes it harder to find breast cancer on a mammogram and also raises the risk of developing breast cancer. 

It is best to have 3D mammograms when you have dense breasts. Talk to your care team about what is best for you. 

Additional screening options, such as MRI, breast ultrasound, or contrast enhanced mammography may be recommended. 

It is important to always know how your breasts normally look and feel even if you have a normal mammogram report. Call your provider right away if you notice any changes in your breasts. 

 

For more information please call your provider. 


Created: 05/2021

Reviewed: 06/2024

Revised: 06/2024