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Breast Cancer

Understanding Your Mammogram Report

A doctor called a radiologist will categorize your mammogram results using a numbered system. 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 standard system to describe mammogram findings and results. This system (called the Breast Imaging Reporting and Data System or BI-RADS) 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 about 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?



What it means


Incomplete - Additional imaging evaluation and/or comparison to prior mammograms (or other imaging tests) is needed.

This means the radiologist may have seen a possible abnormality, but it was not clear and you will need more tests, such as another mammogram with the use of spot compression (applying compression to a smaller area when doing the mammogram), magnified views, special mammogram views, and/or ultrasound. This may also suggest that the radiologist wants to compare your new mammogram with older ones to see if there have been changes in the area over time. 





This is a normal test result. Your breasts look the same (they are symmetrical) with no masses (lumps), distorted structures, or suspicious calcifications. In this case, negative means nothing new or abnormal was found.


Benign (non-cancerous) finding

This is also a negative test result (there’s 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 procedure (such as a biopsy) in the breast. 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 since it’s not proven to be benign, it’s helpful to be extra safe and see if the area in question does change over time.

You will likely need follow-up with repeat imaging in 6 to 12 months and regularly after that until the finding is known to be stable (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 do not definitely look like cancer but could 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 (or ultrasound or MRI) that have already been shown to be cancer by a previous biopsy. Imaging may 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 denser your breasts, 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, which are described in Breast Density and Your Mammogram Report.

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.

American College of Radiology. ACR BI-RADS ATLAS – Mammography. Reporting System, 2013. Accessed at  on September 30, 2021.

Helvie MA, Patterson SK. Chapter 11: Imaging Analysis: Mammography. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2014. 

Venkataraman S, Slanetz PJ, Lee CI. Breast imaging for cancer screening: Mammography and ultrasonography. UpToDate. 2021. Accessed at on September 30, 2021.

Last Revised: January 14, 2022

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