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What are Dense Breasts?


Amber Nason • Oct 12, 2016

One of the risk factors for breast cancer is dense breast tissue. In fact, the Canadian Cancer Society states that the cancer risk for women with dense breast tissue in 75 percent or more of their breasts increases by four to six times, compared to women with little or no dense breast tissue. 

At Mayfair Diagnostics all of our mammography machines are equipped with software that classifies breast density, which is included in reports to referring doctors.


You can't tell by looking at them, whether or not you have dense breasts. It is a clinical diagnosis that can only be assessed by mammography. Dense breasts have less fat and more glandular and connective tissue. Unfortunately, they also make a mammogram harder to read, so smaller cancers may be hidden. Plus, the denser the breast tissue, the higher the risk of breast cancer.

On a mammogram, fatty tissue looks dark, while both dense tissue and tumours look white, making it hard to distinguish between the two. The white-looking breast cancers are easier to see on a mammogram when they're surrounded by dark-looking fatty tissue.

Dense breasts are normal. Your breast tissue changes as you age, usually becoming less dense as you get older and go through menopause, but some women continue to have dense breast regardless of age. Dense breasts may also run in families and be affected by taking hormone replacement therapy.


To determine your breast density, you will need to discuss scheduling a mammogram and a review of the results with your health care provider.

The Breast Imaging Reporting and Database Systems, or BI-RADS, classifies breast density into four groups:

  • Mostly fatty: Mostly fat and with little dense tissue.
  • Scattered density: Quite a bit of fat with a few areas of dense tissue.
  • Consistent density: Many areas of dense tissue evenly distributed through the breasts.
  • Extremely dense: A lot of dense tissue. This may make it hard to see a cancer on a mammogram because the cancer can blend in with the normal tissue.

While scoring is not an exact science and radiologists often disagree about levels of density, it is important to get screened. Mayfair uses the Volpara Health Technologies program which scores density from A to D and we will explain your breast score at the end of your appointment. 


When an assessment determines that breast density is high, the radiologist may suggest annual mammography exams. In addition, the radiologist may suggest the use of Automated Breast Ultrasound (ABUS) or 3D mammography, such as Tomosynthesis, in conjunction with your regular screening mammogram.

Tomosynthesis views the breast in slices and provides a greater level of detail, while ABUS increases the sensitivity of the scan. The 2013 Toward Optimized Practice Breast Cancer Screening Guidelines suggest that ultrasound “may have a role as an adjunct to mammography screening in women with dense breasts, as determined by a radiologist.” You will need to discuss your results and next steps with your health care provider.

Mayfair offers Tomosynthesis at all of our mammography locations,  and ABUS locations can be viewed here


Auntminnie.com article “ABUS shown to improve cancer detection in women with dense breasts

Breastcancer.org – Risk Factors: Dense Breasts

Canadian Breast Cancer Foundation – Know Your Risk: Breast Density

Canadian Cancer Society: http://www.cancer.ca/en/cancer-information/cancer-type/breast/risks/?region=bc#dense_breast

Public Health Agency of Canada. (2009) Information on Mammography for Women Aged 40 and Older: A Decision Aid for Breast Cancer Screening in Canada. Chronic Disease Management Division, Centre for Chronic Disease Prevention and Control.

Toward Optimized Practice. (2013) Breast Cancer Screening Clinical Practice Guidelines. September:

White, J. (2000) “Breast Density and Cancer Risk: What is the Relationship?” Journal of the National Cancer Institute. 92 (6): 443


Breast Health, Disease Prevention