Medically reviewed by Ethan Rogers, MD.
The Breast Imaging Reporting and Data System (BI-RADS) was developed by the American College of Radiology to standardize and simplify the reporting of complex mammogram findings. It ensures that radiologists can clearly communicate results to you and your doctor. By breaking down your imaging results, BI-RADS helps guide the next steps in your care plan.
What Is the BI-RADS System?
BI-RADS organizes findings from mammograms, breast ultrasounds and breast MRIs into clear, consistent categories. These categories help radiologists provide clear recommendations and guide the next steps in your care.
Your mammogram report may simplify results to phrases like “no evidence of cancer,” but the version sent to your doctor includes a BI-RADS number. This score offers insight into your imaging results and informs the care plan you and your doctor will discuss.
Decoding Your BI-RADS Score
BI-RADS scores range from 0 to 6.
Category 0: Incomplete—More Imaging Needed
The radiologist needs additional information, such as prior images or supplemental ultrasounds or MRIs.
Next steps: You should schedule additional imaging.
Category 1: Negative
The radiologist found no abnormalities, masses or suspicious calcifications.
Next steps: You can continue with regular screenings.
Category 2: Benign Finding
The radiologist sees noncancerous findings such as simple cysts or benign (noncancerous) calcium deposits, which are common as you get older.
Next steps: You can continue with routine screenings.
Category 3: Probably Benign—Short-Interval Follow-Up Suggested
The radiologist found something abnormal, but it’s unlikely to be cancer. Still, your doctor will want to have additional follow-up testing to make sure there are no changes over time.
Next steps: You should have follow-up imaging, which is typically recommended in six months and monitored for two years.
Category 4: Suspicious Abnormality—Biopsy Recommended
Your mammogram showed an area of concern that may indicate cancer.
Subcategories on the report indicate the level of suspicion:
- 4A: Low likelihood (2%–10%)
- 4B: Moderate likelihood (10%–50%)
- 4C: High likelihood (50%–95%)
Next steps: The radiologist strongly recommends a biopsy.
Category 5: Highly Suggestive of Malignancy (Cancer)
Your mammogram found something abnormal, and there is at least a 95% chance of cancer.
Next steps: You should schedule a biopsy and possibly a surgical consultation.
Category 6: Known Biopsy—Proven Malignancy
Doctors use this category when someone has been diagnosed with cancer but hasn’t had the tumor surgically removed.
Understanding Breast Density
Your report will also include an assessment of breast density—the proportion of fibrous and glandular tissue compared to fatty tissue. Breast tissue is made up of three main types: fibrous, glandular and fatty tissue. Fibrous tissue gives the breast its shape and structure, glandular tissue is responsible for producing milk, and fatty tissue cushions the breast and fills the spaces between. Breast density falls into four categories:
- A: Fatty tissue (least dense)
- B: Scattered density
- C: Heterogeneously dense (a combination of dense and fatty tissue, with more dense tissue)
- D: Extremely dense (most dense)
Dense breast tissue (categories C and D) can slightly increase breast cancer risk and make abnormalities harder to see on an imaging exam. The U.S. Food and Drug Administration requires mammography facilities to include breast density information in reports. If your report indicates that you have dense tissue, talk with your doctor about any additional imaging you may need, such as breast MRIs.
Take Charge of Your Health
Understanding your BI-RADS report can help clarify the breast imaging process and guide next steps. While medical results can be stressful, knowledge is power. Routine screenings, follow-ups and conversations with your doctor are essential to maintaining good breast health.