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Understanding Your Mammogram Report
The radiologist, a doctor who diagnoses diseases and injuries using imaging tests, will categorize your mammogram results using a numbered system called BI-RADS. Talk to your doctor about your mammogram results and what you need to do next.
What is a BI-RADS assessment category?
Doctors use a system called the Breast Imaging Reporting and Data System or BI-RADS to describe mammogram findings and results. This system sorts the results into categories numbered 0 through 6.
With these categories, doctors can describe what they find on a mammogram using the same words and terms. This makes communicating the test results and following up after the tests easier.
Note: These same BI-RADS categories can also be used to describe the results of a breast ultrasound or breast MRI exam. However, the recommended next steps after these tests might be slightly different.
What do the BI-RADS categories mean?
Incomplete: Additional imaging evaluation and/or comparison to prior mammograms or other imaging tests is needed.
The radiologist might have seen a possible abnormality, but it was not clear. This means you will need more tests, such as:
- Another mammogram with spot compression (applying compression to a smaller area when doing the mammogram)
- Magnified views
- Special mammogram views
- Ultrasound
This might also suggest that the radiologist wants to compare your new mammogram with older ones to see if there have been changes in an area over time.
Negative
This is a normal test result. Negative means nothing new or abnormal was found. Your breasts look the same (they are symmetrical) with no masses (lumps), distorted structures, or suspicious calcifications.
Benign (noncancerous) finding
This means there is no sign of cancer, but the radiologist chooses to describe a finding that is not cancer, such as benign calcifications, masses, or lymph nodes in the breast. This can also be used to describe changes from a prior breast procedure, such as a biopsy. This ensures that others who look at the mammogram in the future will not misinterpret the benign finding as suspicious.
Probably benign finding: Follow-up in a short time frame is suggested.
A finding in this category has a very low (no more than 2%) chance of being cancer. It is not expected to change over time, but it should be checked to be safe. You will likely need follow-up with repeat imaging in 6 to 12 months and regularly after that until the area has not changed for a while (usually at least 2 years).
This approach helps avoid unnecessary biopsies, but if the area does change over time, it still allows for early diagnosis.
Suspicious abnormality: Biopsy should be considered.
These findings might or might not be cancer. The radiologist is concerned enough to recommend a biopsy. The findings in this category can have a wide range of suspicion levels. For this reason, this category is often divided further.
- 4A: Finding with a low likelihood of being cancer (more than 2% but no more than 10%)
- 4B: Finding with a moderate likelihood of being cancer (more than 10% but no more than 50%)
- 4C: Finding with a high likelihood of being cancer (more than 50% but less than 95%), but not as high as Category 5
Highly suggestive of malignancy: Appropriate action should be taken.
The findings look like cancer and have a high chance (at least 95%) of being cancer. Biopsy is very strongly recommended.
Known biopsy-proven malignancy: Appropriate action should be taken.
This category is only used for findings on a mammogram, ultrasound, or MRI that have already been shown to be cancer by a previous biopsy. Imaging might be used in this way to see how well the cancer is responding to treatment.
BI-RADS reporting breast density
Your mammogram report will also include an assessment of your breast density, which is a description of how much fibrous and glandular tissue is in your breasts, as compared to fatty tissue. The more dense your breasts are, the harder it can be to see abnormal areas on mammograms. Having dense breasts also slightly raises your risk of getting breast cancer.
BI-RADS classifies breast density into 4 groups (A to D), which are described in Breast Density and Your Mammogram Report.
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- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
American College of Radiology. American College of Radiology Breast Imaging Reporting and Data System BI-RADS, 5th ed, D'Orsi CJ, Sickles EA, Mendelson EB, Morris EA, et al. (Eds), American College of Radiology, Reston, VA 2013.
Slanetz PJ, Lee CI. Breast imaging for cancer screening: Mammography and ultrasonography. UpToDate. 2026. Accessed at https://www.uptodate.com/contents/breast-imaging-for-cancer-screening-mammography-and-ultrasonography on April 7, 2026.
Last Revised: July 23, 2026
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
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