The Breast Imaging Data Reporting System (BI-RADS®) was created by the American College of Radiology as a way for radiologists to report mammogram results. A radiologist looks at your mammogram and gives it a rating that is understood by your provider. This system is used to tell if any changes were seen and how serious they may be. Your results can be found in your mammogram report and may have information about your BIRAD category, breast density, and if there is a need for follow-up.
The categories, 0-6, use standard wording to describe mammogram findings. This makes sharing the results with providers and patients easier to understand.
Category 0
Need Additional Imaging Evaluation and/or Prior Mammograms for Comparison: More imaging is needed. The mammogram will likely need to be redone. The image may have been blurry or not clear.
Category 1
Negative: This means nothing abnormal was seen. There is nothing to comment on. The breasts are symmetric (look the same), and have no masses, unusual appearance, or suspicious calcifications (calcium deposits). You should follow routine guidelines for when to have your next mammogram.
Category 2
Benign Finding(s): Like Category 1, this result is normal, but there is something benign (abnormal, but not cancerous) seen. This could be a few things including cysts, lymph nodes, adenomas, changes related to prior surgery or implants. There is no sign of cancer.
Category 3
Probably Benign Finding - Follow-up in a shorter time frame is suggested: This means something abnormal was seen that the radiologist is pretty sure is not cancer. You should watch this area closely with a repeat mammogram in 6 months to see if the area changes. Abnormalities of this category have less than a 2% risk of malignancy (being cancer). By watching the area closely, you can avoid having biopsies that are not needed. If the area changes, further testing will be done.
Category 4
Suspicious Abnormality - Biopsy Should Be Considered: This category covers a wide range of findings. It means there is an area that does not clearly look like cancer, but the radiologist suggests a biopsy to be sure. This category may be further classified to make the level of concern clearer:
Category 5
Highly Suggestive of Malignancy - Appropriate Action Should Be Taken (Almost certainly cancerous): These findings have a very high chance (>95%) of being cancer. A biopsy is needed.
Category 6
Known Biopsy - Proven Malignancy - Appropriate Action Should Be Taken: This category is used when there is already a diagnosis of cancer.
Breast Density
The mammogram report will also have information about your breast density. Dense breast tissue is made up of more fibrous or glandular tissue than fatty tissue. Having dense breast tissue is common (found in about 40% of women) and not abnormal. If you have dense breasts, they can change (and get less dense) as you get older.
Dense breast tissue can make it harder for the radiologist to read the mammogram. Your report may tell you the extent of the dense tissue in one of 4 categories (A-D):
Dense breast tissue leads to an increased risk of breast cancer. This has led to laws requiring women to be told of their breast density. If your report shows dense breast tissue (categories C & D), you should talk with your provider about your breast cancer screening plan. Studies have found that a 3D mammogram (also called tomosynthesis) or breast MRI may be better at finding abnormalities in women with dense breast tissue.
Mammograms cannot always tell the difference between something abnormal that is cancer and something abnormal that is not cancer. It is best to find breast cancer early. When a radiologist looks at your mammogram, if there is anything they feel unsure about, they will want to look further. That often means coming back for more mammogram images. If there are still questions, they may do an ultrasound.
About 10% of women will be called back to have repeat mammograms or ultrasound to look again at something. This percentage is higher in younger women (especially those younger than 40 years of age) and those having their first mammogram. Breast tissue of younger women tends to be denser and there is no previous mammogram to compare it to. This makes it harder for the radiologist to read the current mammogram. It is important to remember that only about 3 out of every 1,000 mammograms lead to a cancer diagnosis.
Of the 10% of women who return for a repeat mammogram, only 8-10% of those will need a biopsy for more testing. About 80% of breast biopsies turn out to be benign.
It can be very stressful waiting for tests and results, so be sure to talk with your care team about your concerns and any questions you may have.
ReferencesBakker, M. F., de Lange, S. V., Pijnappel, R. M., Mann, R. M., Peeters, P. H., Monninkhof, E. M., . & de Jong, M. D. (2019). Supplemental MRI Screening for Women with Extremely Dense Breast Tissue. New England Journal of Medicine, 381(22), 2091-2102.
D’Orsi CJ, Sickles EA, Mendelson EB, Morris EA, et al. ACR BI-RADS ® Atlas, Breast Imaging Reporting and Data System. Reston, VA, American College of Radiology; 2013
Ekpo, E. U., Ujong, U. P., Mello-Thoms, C., & McEntee, M. F. (2016). Assessment of interradiologist agreement regarding mammographic breast density classification using the fifth edition of the BI-RADS atlas. American Journal of Roentgenology, 206(5), 1119-1123.
Rafferty, E. A., Durand, M. A., Conant, E. F., Copit, D. S., Friedewald, S. M., Plecha, D. M., & Miller, D. P. (2016). Breast cancer screening using tomosynthesis and digital mammography in dense and nondense breasts. Jama, 315(16), 1784-1786.