Breast Imaging, Reporting & Data System (BIRADS)
The Breast Imaging Data Reporting System (BI-RADS®) was developed by the American College of Radiology as a way to standardize how mammogram results are reported by radiologists. The radiologist reviews the mammogram films and gives them a rating, which is easily understood by the referring provider. The rating system is used to tell if any abnormality was seen and how serious the radiologist thinks it may be. Knowing your BI-RADS score may help you understand how concerned the radiologist is about what they see. This score is usually found in the mammogram report.
Need Additional Imaging Evaluation and/or Prior Mammograms for Comparison: In this category, more imaging is needed to assign a score. This is considered an incomplete test. Perhaps the image was blurry or unclear and more pictures are needed.
Negative: This means nothing abnormal was seen. There is nothing to comment on. The breasts are symmetric (look the same), and no masses, unusual appearance, or suspicious calcifications are seen. You should follow routine guidelines for when to have your next mammogram.
Like Category 1, this result is considered normal, but here, there is something benign (abnormal, but not cancerous) seen. This could be a number of different things including cysts, lymph nodes, adenomas, changes related to prior surgery or implants. However, there is no sign of cancer.
Probably Benign Finding - Follow-up in a shorter time frame is suggested:
This means something abnormal was seen that the radiologist is pretty certain is not cancer. It is recommended to watch this area closely with a repeat mammogram in 6 months to see if the area changes. Abnormalities assigned to this category have less than a 2% risk of malignancy. By watching the area closely, you can avoid unnecessary biopsies. If the area changes, further testing will be done.
Suspicious Abnormality - Biopsy Should Be Considered:
This category sounds scary but really covers a wide range of findings. It means there is an area that does not definitely look like cancer, but the radiologist is concerned and recommends a biopsy to be sure. This category includes a wide range of suspicion and may be further classified to make the level of concern clearer. This may include:
4A – Radiologist believes there is a low chance of the area being cancer (2-10% chance).
4B – Radiologist believes there is a medium chance of the area being cancer (10-50%).
4C - Radiologist believes there is a high chance of the area being cancer (50-95%).
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.
Known Biopsy - Proven Malignancy - Appropriate Action Should Be Taken:
This category is reserved for areas seen on the mammogram when there has already been a diagnosis of cancer.
The mammogram report will also include 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):
- A: No dense tissue (all fatty tissue).
- B: Scattered areas of dense tissue.
- C: Mostly dense (called heterogeneously dense).
- D: Extremely dense.
Dense breast tissue is associated with an increased risk of breast cancer. This has led to laws requiring that women be notified of their breast density. If your report shows dense breast tissue (categories C & D), you should discuss your breast cancer screening plan. Studies have found that a 3D mammogram (also called tomosynthesis) or breast MRI may better detect abnormalities in women with dense breast tissue.
Mammogram Call Backs
Mammogram is an imperfect test as it often cannot tell the difference between something abnormal that is cancer and something abnormal that is not cancer. But it is the best we have to detect breast cancer early. When a radiologist looks at your pictures, if there is anything they feel uncertain about, they will want to look further. That usually means coming back for more mammogram images. Using the same machine, the technologist will take pictures from different angles. If those pictures don’t clear things up for the radiologist, they may do an ultrasound.
About 10% of women will be called back to have repeat mammograms or ultrasound to clarify something seen on the first test. This percentage is higher in younger women (particularly those below 40 years of age) and those having their first mammogram. This is because the breast tissue of younger women tends to be denser and there is a lack of a previous film to compare to in first-timers. This makes it more difficult for the radiologist to read the current mammogram. It is important to remember, only approximately 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 further testing. And about 80% of breast biopsies turn out to be benign. The bottom line is, don't put the cart before the horse. It can be very stressful waiting for tests and results, but the odds are in your favor, so hang in there!
American Cancer Society. Understanding Your Mammogram Report. https://www.cancer.org/cancer/breast-cancer/screening-tests-and-early-detection/mammograms/understanding-your-mammogram-report.html
Bakker, 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.