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American Family Children's Hospital

Dense Breast Tissue

Breast specialists at UW Health's Breast Center can identify dense breast tissue, which is more fibrous and thick and less fatty than non-dense breast tissue, during mammogram examination.


What is dense breast tissue?


Breast tissue is made up of:

  • Milk glands or lobules
  • Milk ducts and supportive/connective tissue
  • Fatty tissue

A radiologist defines the amount of dense and non-dense breast tissue while examining a mammogram. Dense breast tissue, which is more fibrous or thick and less fatty, shows up as a solid white area, similar to how cancer may appear on a mammogram. (Fatty tissue appears dark and transparent.)


Dense tissue may make screening for breast cancer more difficult, and can increase the risk that cancer will not be detected when it is at a smaller size. Women with dense breast tissue also have a higher risk of developing cancer, but the reason why remains unclear.


How will I know that I have dense breasts?


The density of your breasts is defined on a mammogram and may change throughout your lifetime. There is no relationship between breast size and density. You can’t tell how dense your breasts are by doing an exam.


What causes dense breast tissue?


Around 10 percent of women who undergo mammogram testing will learn they have extremely dense breasts, but most women—around 80 percent—either have a range of tissue density, or scattered areas of density. Women who are more likely to have dense breast tissue:

  • Are in their 40s and 50s
  • Are premenopausal
  • Take combination hormone therapy to treat symptoms of menopause

How can I protect my health if I have dense breast tissue?


A mammogram is still the best way to detect changes in your breasts and catch cancer as early as possible. Digital Breast Tomosynthesis, or 3-D mammograms, provide radiologists and patients with better ways to see changes even in dense breast tissue. Your doctor may recommend that you have yearly screening mammography if you have dense breasts.


There is no evidence that additional tests, such as ultrasound or MRI, improve detection or survival rates. They may detect more cancers, but can also generate false positives and can carry additional health risks. Talk to your doctor to learn more about risks and benefits of mammography and routine screenings.


BIRADS (Breast Imaging Reporting and Data System) Scales 


The scales below are used to standardize reporting and categorize breast density.




Percent of Women


Breast tissue almost entirely fatty



Scattered areas of fibroglandular density in the breast



Breasts are heterogeneously dense



Breasts are extremely dense