BI-RADS (Breast Imaging Reporting and Data System) is a standardized scoring system (Categories 0–6) used by radiologists to describe mammogram findings and guide follow-up care. A BI-RADS category is not a breast cancer diagnosis or cancer stage. Most results (BI-RADS 1–3) indicate normal or likely benign findings, while higher categories (BI-RADS 4–5) recommend a tissue biopsy to rule out malignancy.
 

What is BI-RADS?
According to the American College of Radiology (ACR), BI-RADS stands for Breast Imaging Reporting and Data System. It provides standardized terminology and assessment categories for mammography, breast ultrasound and breast MRI.
Each examination receives an assessment category that communicates how concerning a finding appears and whether routine screening, additional imaging, short-term follow-up or biopsy may be appropriate.
 

What do BI-RADS categories 0–6 mean?
Radiologists assign a specific BI-RADS category based on visual features in your scan. The table below outlines what each category means, the estimated likelihood of cancer, and typical next steps:
 

BI-RADS category	What it means	Estimated likelihood of malignancy	Typical next step	What patients should know
BI-RADS 0 – Incomplete	The examination cannot yet receive a final assessment because more information is needed.	Not assigned	Additional mammogram views, breast ultrasound and/or comparison with previous imaging	BI-RADS 0 does not mean cancer. A final category is usually assigned after further evaluation.
BI-RADS 1 –Negative	No suspicious abnormality is identified.	No suspicious finding identified	Routine breast screening according to age, risk and medical recommendations	This is a normal imaging assessment.
BI-RADS 2 – Benign	A clearly noncancerous finding is present, such as certain cysts or benign calcifications.	Essentially benign	Routine screening	The finding is documented but does not have suspicious imaging characteristics.
BI-RADS 3 – Probably benign	The finding is very likely benign but should be monitored to confirm stability.	≤2%	Short-interval follow-up imaging, often beginning at about six months	Follow-up is important because stability over time supports a benign assessment.
BI-RADS 4 – Suspicious	The finding has enough suspicious features that tissue diagnosis is generally recommended.	>2% to <95%	Image-guided biopsy is generally recommended	BI-RADS 4 does not confirm cancer. The category covers a broad range of risk and may be divided into 4A, 4B and 4C.
BI-RADS 4A – Low suspicion	Mildly suspicious imaging features	>2% to 10%	Biopsy generally recommended	Most findings in this category will still prove benign, but tissue diagnosis is usually needed.
BI-RADS 4B – Moderate suspicion	Imaging features raise an intermediate level of concern	>10% to 50%	Biopsy generally recommended	Pathology is needed to determine whether the finding is benign or malignant.
BI-RADS 4C – High suspicion	Imaging features are substantially concerning but do not meet BI-RADS 5 criteria	>50% to <95%	Biopsy strongly indicated	The probability of cancer is higher, but only tissue diagnosis can confirm malignancy.
BI-RADS 5 – Highly suggestive of malignancy	Imaging findings have classic or highly concerning features for cancer.	≥95%	Biopsy and appropriate clinical action	Cancer is highly suspected, but biopsy is still required to establish the diagnosis.
BI-RADS 6 – Known biopsy-proven malignancy	Cancer has already been confirmed by tissue diagnosis.	Malignancy already confirmed	Imaging may support treatment planning and assessment	This category is used for a cancer that has already been diagnosed, not for estimating whether cancer is present.

 

What happens after an abnormal mammogram?
An abnormal mammogram does not automatically mean breast cancer. The next step depends on the BI-RADS category, the specific imaging finding and your individual risk factors.
 
Further evaluation may include:

• Additional diagnostic mammogram views
• Breast ultrasound
• Breast MRI in selected situations
• Comparison with previous breast imaging
• Image-guided core needle biopsy when tissue diagnosis is needed

Your medical team may also consider breast density, symptoms, age, family history, personal medical history and previous imaging before recommending further investigation.
 

Is BI-RADS the Same as Breast Density?
No. BI-RADS assessment categories and breast density describe different aspects of a mammogram.
 

• BI-RADS category: Describes the radiologist’s assessment of specific imaging findings and helps determine the appropriate next step, such as routine screening, additional imaging, follow-up or biopsy.
• Breast density: Describes the proportion of fibrous and glandular tissue compared with fatty tissue in the breast.

 
Breast density is classified into four categories:

• A: Almost entirely fatty
• B: Scattered areas of fibroglandular density
• C: Heterogeneously dense
• D: Extremely dense

 
Dense breast tissue can make some abnormalities more difficult to detect on mammography. Breast density may therefore be considered together with age, family history and other breast cancer risk factors when determining an individualized screening approach.
 

Why Choose Bumrungrad International Hospital for Mammography and Breast Care?
At Bumrungrad International Hospital, the Breast Center works with the Diagnostic Radiology and Nuclear Medicine Center and Horizon Regional Cancer Center to support breast screening, diagnosis and treatment.
Multidisciplinary care may involve breast radiologists, breast surgeons, pathologists, medical oncologists, radiation oncologists, and other specialists according to each patient’s needs.
 

• Advanced Diagnostics:

Bumrungrad offers advanced breast imaging and diagnostic services, including 3D digital mammography, breast ultrasound, breast MRI, stereotactic and other image-guided breast biopsies. The hospital also uses Lunit INSIGHT MMG, an AI-assisted mammography system that analyzes mammographic images and highlights suspicious areas for closer evaluation. AI supports the radiologist’s interpretation rather than replacing specialist review.
 

• Internationally Accredited Care:

Bumrungrad’s Breast Cancer Program received Joint Commission International Clinical Care Program Certification (JCI CCPC) in 2025, recognizing its commitment to international standards for quality and patient safety in breast cancer diagnosis and treatment.
 

• Global Recognition:

In Newsweek and Statista’s Best Specialized Hospitals Asia Pacific 2026, Bumrungrad ranked No. 1 in Thailand and 58th in Asia-Pacific for Oncology. Bumrungrad was also ranked No. 96 worldwide in Newsweek’s World’s Best Hospitals 2026, remaining the only hospital from Thailand in the global Top 100.


Frequently Asked Questions

Does BI-RADS 3 mean cancer?
No. BI-RADS 3 means a finding is probably benign, with no more than a 2% likelihood of malignancy. Follow-up imaging is typically recommended to confirm that the finding remains stable.
 
Does BI-RADS 4 mean I have breast cancer?
No. BI-RADS 4 means the finding is suspicious enough that a biopsy is generally recommended. The biopsy determines whether the tissue is benign or malignant.
 
Which BI-RADS categories usually require a biopsy?
BI-RADS 4 and BI-RADS 5 findings generally require biopsy or other appropriate diagnostic action. BI-RADS 4 represents a suspicious finding, while BI-RADS 5 is highly suggestive of malignancy.
 
Can a BI-RADS category change after additional imaging?
Yes. BI-RADS 0 means the assessment is incomplete. After additional mammogram views, ultrasound or comparison with previous images, the radiologist can assign a final BI-RADS category.
 
Is BI-RADS a breast cancer stage?
No. BI-RADS describes breast imaging findings and recommended next steps. Breast cancer staging is performed only after cancer has been diagnosed.
Understanding your BI-RADS mammogram result can make the report easier to interpret. Rather than viewing the number as a diagnosis, think of it as a standardized guide that helps you and your healthcare team decide what should happen next.
 
 
References

1. Newell MS, Destounis SV, Leung JWT, DeMartini WB, Lee CH, Eby PR. ACR BI-RADS® v2025 Manual. Reston, VA: American College of Radiology; 2025.
2. Spak DA, Plaxco JS, Santiago L, Dryden MJ, Dogan BE. BI-RADS® fifth edition: A summary of changes. Diagnostic and Interventional Imaging. 2017;98(3):179–190.
3. Mercado CL. BI-RADS update. Radiologic Clinics of North America. 2014;52(3):481–487.
4. Bent CK, Bassett LW, D'Orsi CJ, Sayre JW. The positive predictive value of BI-RADS microcalcification descriptors and final assessment categories. American Journal of Roentgenology. 2010;194(5):1378–1383.
5. Boyd NF, Guo H, Martin LJ, et al. Mammographic density and the risk and detection of breast cancer. New England Journal of Medicine. 2007;356(3):227–236.
6. McKinney SM, Sieniek M, Godbole V, et al. International evaluation of an AI system for breast cancer screening. Nature. 2020;577(7788):89–94.

 

Medically reviewed by:
Piyawan Kensakoo, M.D.
Breast Surgery & General Surgery
Last medically reviewed: September 2026