Breast density refers to the amount of normal, non-fatty tissue visible in a woman’s breasts on mammograms. Washington state law now mandates that women be directly notified if they have dense breast tissue on a screening mammogram.
There are four categories of breast density: almost entirely fat, scattered fibroglandular, heterogeneously dense, and extremely dense. If your patients’ breasts are in the higher two categories (heterogeneously or extremely) they are considered “dense.”
Mammograms can be less accurate in women with dense breasts. The dense tissue looks white on mammograms and can appear similar to breast masses or tumors. Breast density also has been linked to an increase in future risk of developing breast cancer, though it is important to note that breast density alone has only a small impact on breast cancer risk.
The table below provides relative risks for developing breast cancer by density category*.
*Source: Annals of Internal Medicine: Benefits, Harms, and Cost-Effectiveness of Supplemental Ultrasonography Screening for Women With Dense Breasts
Seattle Cancer Care Alliance mammograms and breast density
The below chart breaks down breast density type from SCCA mammogram patients from 2015 to 2017.
We recognize that notifying patients of their breast density may lead patients to have questions on what they should do next. Every woman who receives a mammogram at the SCCA or University of Washington Medicine will receive an information pamphlet on breast density. To assist you with counseling your patient, we encourage you to discuss the following with your patients:
- Reassure your patient that screening mammograms, particularly those with 3D technology, also known as tomosynthesis, remain useful for detection of breast cancer regardless of their density.
- Explain your patient that the data are not clear on whether supplemental screening of women with dense breasts with additional imaging tests provide greater benefit than harm. The most commonly discussed supplemental examinations are ultrasound and MRI. The UW/SCCA is actively involved in research studies on identifying optimal supplemental screening exams for patients with dense breasts. More information on our active research trials can be found here.
- Talk with your patient to see if there is anything besides breast density that may increase her risk for getting breast cancer. Women at higher breast cancer risk as determined by a risk assessment model that appropriately weights family history may be eligible for supplemental screening with breast MRI. This approach is supported by robust evidence.
When to refer for additional screening
You are encouraged to perform your patients' risk assessment using the Breast Cancer Surveillance Consortium Risk Calculator.
- If the resultant risk is greater than 2.5 percent at five years, you may consider a referral to the SCCA Breast Health Clinic or the UW Roosevelt Women's Clinic for additional risk assessment and counseling.
- If the resultant risk is less than 2.5 percent at five years, your patient should continue to get yearly mammograms, particularly ones with tomosynthesis technology.
Refer your patient
Our breast health experts provide breast cancer screenings and can help you figure out which screenings are right for your patient based on age, health, risk level and other factors.
Breast Health Clinic at SCCA – South Lake Union
Phone: (206) 606-2166
Fax: (206) 606-6994
Women's Health Care Center at UWMC – Roosevelt
Phone (206) 598-7749
Fax: (206) 598-6048