Dense Breast

What is breast density?

Breast density refers exclusively to the way the breast looks on a mammogram. It has no relationship to the way the breast looks or feels on physical exam. Your breasts are considered dense if you have more fibrous or glandular tissue and not much fat.

Breast density is categorized into one of four categories, defined by the American College of Radiology:

  • 1/A The breast is almost entirely fatty. 2/B There are scattered fibroglandular densities.
  • 3/C The breast tissue is heterogeneously dense, which may obscure small masses. (40 percent of women)
  • 4/D The breast tissue is extremely dense. This may lower the sensitivity of mammography. (10% of women)

Approximately 50% of women undergoing screening mammography are classified as having either
“heterogeneously dense” or “extremely dense” breasts. A letter is sent to all Spectrum Health mammography patients with their test results, notifying them whether or not they have dense breasts.

Why is breast density important?

Dense tissue appears white on a mammogram. Lumps, both benign and cancerous, also appear white. Dense breasts make it more difficult for doctors to spot cancer on mammograms. 

Mammograms can be less accurate in women with dense breasts. Masking occurs when breast tissue obscures a cancer. While masking is not a substantial problem in patients with non-dense breasts, mammography accuracy is reduced up to 10% to 20% in dense breasts. 

Should I have additional testing if I have dense breasts?

The recommendations for screening mammography are exactly the same for women with dense breasts as for the rest of the population. Mammography is the only screening method that has undergone randomized controlled trials and is proven to reduce breast cancer deaths.Tomosynthesis (3-D mammography) is also available. Studies indicate an increase of 40% to 50% in cancer detection with tomosynthesis, as well as a decrease in the need to return for additional imaging.

What other breast imaging options are available?

Other breast imaging screening options include screening magnetic resonance imaging (MRI), contrast enhanced mammography and ultrasound. MRI has been demonstrated to be a useful screening tool
in patients at very high risk for breast cancer (>20% lifetime risk) based on American Cancer Society guidelines. Studies have shown a modest increase in cancer detection with breast ultrasound, and a high rate of false positives resulting in unnecessary biopsies.

Mammograms can detect breast cancers that are not visible on ultrasound. The choice to have ultrasound should be made on an individual basis after a discussion of the risks, benefits and costs. Ultrasound is used in addition to mammography and a physical exam in problem-solving situations, and not as a screening tool. Also, the cost of the MRI and/or ultrasound may not be covered by insurance.
While other imaging options, such as breast-specific gamma imaging and contrast-enhanced mammography, show promise, they are currently not accepted as proven technologies and are not the standard of care. 

Will I have a risk assessment?

All Spectrum Health Lakeland in the High Risk Cancer Program patients receive a risk assessment at the time of their visit. If you are determined to be at high risk of developing breast cancer you will receive information and/or a referral to our High Risk Cancer Program.

We encourage you to discuss your options with your health care provider or call our High Risk Cancer Program at 269.932.9337 or send an email to

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