The Pink Journey Foundation

Breast Density


A recently published study concluded that breast density “eclipses all other known breast cancer risk factors” for developing breast cancer (ref. 1). A mammogram is required to determine a women’s breast density status (ref. 2-3). Sixty percent of women under the age of fifty have dense breasts.

Early-stage breast cancers are more difficult to detect in women with dense breasts. One recent study found that 98% of breast cancers that were not detected on the screening mammogram occurred in women with dense breasts (ref. 4). In addition, breast cancers arising in dense breast tend to be more aggressive than breast cancers arising in women with a fatty pattern on their mammograms (ref. 5-7).

Why are breast cancers so difficult to detect in dense breasts?

Dense breasts are composed primarily of fibrous and glandular that appears white on the mammogram. Small breast cancers are also white on the mammogram. These small white cancers blend into the white background tissue. Detecting a small cancer in a woman with dense breasts is often compared to the challenge of detecting a snowman in a snowstorm.

Fatty breast tissue is black on the mammogram. It is relatively easy to detect a small white cancer in women with a fatty pattern on the mammogram. As a result breast cancers tend to be smaller when detected on the screening mammogram than are cancers detected in women with dense breasts.

Figures 1 and 2 compare the challenge of detecting an early-stage breast cancer in dense breast vs. a fatty breast. Figure 1 shows an obvious small cancer in a fatty breast. Figure 2 is an example of dense breast. The same cancer easily seen in the fatty breast would be extremely challenging to detect in the dense breast.

Screening Guidelines for Women with Dense Beasts:

We recommend that all women should undergo risk assessment in their twenties (breast screening guidelines). Women who are determined to be at high risk based on their family histories should be referred to a risk assessment clinic.

We recommend that all women have a baseline mammogram by age 35. Women who are found to have dense breast are recommended to have a yearly 3D mammogram (ref. 8). We recommend that average risk women with dense breast have a yearly screening breast ultrasound. Women at high risk are advised to have a yearly MRI in addition to their yearly screening mammogram.

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  1. ‘Dense Breasts’ Eclipse All Other Known Breast Cancer Risk Factors
  2. Dense Breasts: Answers to Commonly Asked Questions
  3. Dense breast tissue: What it means to have dense breasts
  4. Mammographically occult breast cancers detected with AI-based diagnosis supporting software: clinical and histopathologic characteristics
  5. Breast Density and Your Mammogram Report
  6. Women With Dense Breasts Have Higher Risk of More Aggressive Cancer
  7. Do Young Women Have Worse Breast Cancer Outcomes? It Seems to Depend on the Cancer’s Characteristics
  8. 3D mammogram – Mayo Clinic