breast density

Breast Density & Mammograms 101

October is Breast Cancer Awareness Month, the perfect time to inform women about breast density. On June 1, 2015, Michigan passed a law requiring doctors to inform patients about their breast density on mammograms. Information about breast density is vital; highly dense breasts can make cancer detection difficult and increase your risk of cancer. This week on Fox 17, Dr. Bitner discusses breast density and its impact on mammograms.

Fact #1: 

Having dense breasts is common and normal. Around 50% of women have breasts, where more than 75% of the tissue volume is made of glandular tissue. A mammogram report is required to classify the results by density level, which can change by cycle, with hormones, and by age. Classifications are as follows: 

  1. Class A: Mostly fatty tissue; 10% of women
  2. Class B: Scattered density, primarily fatty tissue; 40% of women
  3. Class C: Heterogeneously dense with many areas of density; 40% of women
  4. Class D: Extremely Dense; almost all glandular tissue, 10% of women


It is important to remember that density is not the only risk factor for cancer and can be confusing. For example, African-American women are more likely to have Class A or B tissue but a higher risk of cancer, and women of Asian descent tend to have Class C or D tissue and have a lower risk of breast cancer.

Fact #2:

Mammograms are the best tool to detect breast cancer. Mammograms, however, can miss up to 20% of cancers if breast tissue is extremely dense. Sometimes, ultrasounds are ordered for a closer look to ensure the tissue is simply dense and not hiding a small lump. A tomosynthesis, or 3D mammogram, can improve sensitivity and reduce the chance of an ultrasound.  

Fact #3:

A self-breast exam is important to detect changes in your breast tissue. Do a breast exam every month after your period to know what is normal. Call your doctor’s office and get checked out if you experience any of the following: 

  • Breast pain for more than two weeks 
  • Lump(s) on one side of your breast and not the other. Lumps can be the size of a frozen pea. 
  • If pain and lumps last even after your period

Patient Story: 

Jane, 42, received mammograms for the past two years and was ready to get her third. She had a tomo-mammogram and was worried when she got a call that she had to come back for a second look mammogram and an ultrasound. Jane read her report and noticed Density level C and that her mammogram was a BIRADS 0, meaning further imaging was needed. On her second visit, her scans showed an area where tissue was piling in her breast. An ultrasound confirmed that this was normal dense tissue and not cancer. With an updated mammogram of BIRADS 2, Jane understood that density matters when it comes to breast exams. She was grateful for a positive diagnosis and committed to practicing healthy habits (limiting alcohol, maintaining a healthy weight range, and better food choices) to reduce her breast cancer risk.

Health Tip of the Week: 

It’s important to understand your breasts’ “normal.” Breast density can affect cancer scans, and asking your doctor to help you read mammogram reports can provide essential breast health takeaways. If you still need to get your yearly mammogram, schedule one with your provider today! 

Watch the full segment.