Mammograms, low-dose x-rays of the breast, are used for breast cancer screening. Women at an average risk of developing breast cancer should start getting yearly mammogram testing between age 40 and 44 to make sure that breast cancer is caught early [MB1] if it does develop.[1] Mammogram results may reveal that a woman has dense breast tissue. This means the breasts are made up of a lot of glandular or fibrous tissue and not a lot of fat. Many women’s breasts decrease in density as they age, but some women experience little change.[2]

Breast density is divided into 4 categories: fatty, scattered, heterogenous, and extremely dense. Fatty means the breast is almost entirely made up of fat, scattered means there are some areas of dense glandular and fibrous tissue, heterogenous means most of the breast is made up of dense tissue, and extremely dense means almost all of the breast is made up of dense tissue.[2] About 10% of women have fatty breasts, 40% have scattered breasts, 40% have heterogenous breasts, and 10% have extremely dense breasts.[3] The denser a breast is, the harder it is to see and detect tumors with mammogram testing because the dense tissue and tumors both appear white on the images. Women with dense breast tissue are also at a higher risk of developing breast cancer. Despite mammogram testing being less accurate in women with dense breasts, it is still very important because it can detect most breast cancers.[2]

There is not a consensus between doctors on which, if any, additional imaging tests should be done in women with dense breasts. Digital breast tomosynthesis (also known as 3D mammography), ultrasound, and MRI have all been shown to be able to identify some breast cancers that cannot be seen with mammograms. However, ultrasound and MRI may not be covered by insurance and tend to identify more findings that are not cancer such as noncancerous breast conditions [MB2] which can lead to more tests and unnecessary biopsies.[2] 3D mammograms are also typically more expensive than 2D mammograms which may not be covered by insurance and may not be available in all facilities because it is a newer technology.[1] Women with dense breasts that also are at a high risk of developing breast cancer such as women with an inherited gene mutation [MB3] linked to breast cancer (such as the BRCA gene mutations[MB4] ) or strong family history should get an MRI along with their yearly mammogram.[2]

 [MB1]Link to ‘early breast cancer detection’ article

 [MB2]Link to ‘noncancerous breast conditions’ article

 [MB3]Link to ‘inherited gene mutations’ article

 [MB4]Link to BRCA gene mutations’ article

References

1.     American Cancer Society Recommendations for the Early Detection of Breast Cancer https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/american-cancer-society-recommendations-for-the-early-detection-of-breast-cancer.html (accessed Jun 21, 2021).

2.     Breast Density and Your Mammogram Report https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/mammograms/breast-density-and-your-mammogram-report.html (accessed Jun 25, 2021).

3.     What Does It Mean to Have Dense Breasts? https://www.cdc.gov/cancer/breast/basic_info/dense-breasts.htm (accessed Jun 25, 2021).