What is the role of ACR (American College of Radiology) BIRADS (Breast Imaging Reporting and Data System) v2025 in guiding radiologists to categorize and manage breast imaging findings?

ACR BI-RADS v2025: Standardized Breast Imaging Classification System

The ACR BI-RADS system provides a standardized framework for radiologists to categorize breast imaging findings into seven distinct categories (0-6), each with specific malignancy risk estimates and management recommendations that directly guide clinical decision-making. 1

Core BI-RADS Categories and Their Clinical Significance

Category 0: Incomplete Assessment

• Indicates additional imaging evaluation is needed before final assessment can be made 2, 1
• Almost exclusively used in screening situations when spot compression, magnification views, or ultrasound are required 2
• Requires comparison with prior mammograms when available, though radiologists must use judgment on how vigorously to pursue old studies 2

Category 1: Negative

• No abnormalities detected; breasts are symmetric without masses, architectural distortion, or suspicious calcifications 1
• Management: Resume routine annual screening mammography 2, 1

Category 2: Benign Findings

• Definitively benign findings documented (calcifying fibroadenomas, oil cysts, lipomas, intramammary lymph nodes, vascular calcifications, implants, or surgical changes) 1
• Key distinction from Category 1: specific benign findings are described in the report, whereas Category 1 has no findings to describe 2
• Management: Resume routine annual screening mammography 2, 1

Category 3: Probably Benign

• Malignancy risk less than 2% 2, 1, 3
• Critical requirement: Complete diagnostic evaluation must be performed before assigning Category 3; this assessment should not be made on screening examinations alone 2, 3
• Specific qualifying lesions include: non-calcified circumscribed solid masses <2 cm, non-palpable focal asymmetries without malignant features, and rounded punctate calcifications in small groups 3
• Palpable lesions are explicitly excluded from Category 3 designation based on published scientific data 2
• Management protocol: Initial follow-up at 6 months with diagnostic unilateral mammography, then every 6-12 months for 1-2 years 1, 3
• At 12 months, bilateral mammography is recommended for women ≥40 years to ensure annual contralateral breast evaluation 3
• If lesion increases in size or changes characteristics during follow-up, proceed immediately to biopsy rather than continued surveillance 2, 1, 3

Category 4: Suspicious Abnormality

• Wide range of malignancy probability, greater than Category 3 but less than Category 5 2, 1
• Biopsy is the recommended management 1
• Most breast interventional procedures fall within this category 2
• Radiologists should indicate relevant malignancy probabilities to facilitate informed decision-making 2

Category 5: Highly Suggestive of Malignancy

• Malignancy probability ≥95% 2, 1
• Classic findings include spiculated masses or malignant-appearing pleomorphic calcifications 2, 1
• Tissue diagnosis via core needle biopsy is mandatory 1
• Current oncologic management typically requires percutaneous tissue sampling before definitive surgery for sentinel node imaging or neoadjuvant chemotherapy planning 2

Category 6: Known Biopsy-Proven Malignancy

• Reserved for lesions with biopsy-confirmed malignancy prior to definitive treatment 2, 1
• Added in the fourth edition of BI-RADS specifically for tracking purposes 2
• Management follows breast cancer treatment guidelines 1

Critical Clinical Applications

Age-Specific Imaging Algorithms

Women <30 years:

• Ultrasound is the initial imaging modality of choice 2, 4
• Add diagnostic mammography only if ultrasound shows suspicious findings (BI-RADS 4 or 5) or patient has BRCA/genetic mutations 2, 4
• Mammography is not indicated unless clinical findings are highly suspicious 2

Women 30-39 years:

• Either ultrasound or diagnostic mammography/DBT can serve as initial imaging 2, 4
• Sensitivity of ultrasound (95.7%) exceeds mammography (60.9%) in this age group, with similar specificity 2
• If suspicious mass identified on ultrasound, bilateral mammography is recommended 2

Women ≥40 years:

• Diagnostic mammography or DBT is the appropriate initial imaging 2, 4
• Ultrasound is added after mammography if findings are suspicious or if targeted correlation is needed 2

Special Circumstances Warranting Immediate Biopsy of Category 3 Lesions

Despite the low malignancy risk, immediate biopsy of BI-RADS 3 lesions is reasonable in specific clinical scenarios: 2, 3

• High-risk patients (genetic mutations, strong family history) 2, 3
• Patients awaiting organ transplant 2
• Patients with known synchronous cancers 2
• Patients attempting pregnancy 2
• Situations of extreme patient anxiety that biopsy would alleviate 2, 3
• Uncertain follow-up compliance 3

Dense Breast Tissue Considerations

The 2025 ACR guidelines emphasize supplemental screening in dense breasts (heterogeneously dense or extremely dense) 2:

• Women with extremely dense tissue have 4-6 fold increased breast cancer risk compared to fatty tissue 2
• Mammography sensitivity is decreased in dense tissue, with increased interval cancer rates 2
• For intermediate-risk women with dense tissue, breast MRI and abbreviated breast MRI (AB-MRI) are usually appropriate, while ultrasound and contrast-enhanced mammography may be appropriate 2
• For high-risk women, breast MRI or AB-MRI is usually appropriate regardless of density 2

Essential Documentation Principles

Cumulative Assessment

• When multiple imaging modalities are performed (mammography and ultrasound), the BI-RADS category represents cumulative findings from both studies 1
• The overall assessment is based on the most worrisome finding when multiple abnormalities are identified 1

Dynamic Reassessment

• BI-RADS categories may change based on subsequent imaging findings 1
• Categories can increase, decrease, or remain stable depending on lesion evolution 1

Pathology-Imaging Concordance

• When biopsies are performed, pathology-imaging concordance is essential 1
• If pathology and imaging are discordant, repeat imaging and/or additional tissue sampling is mandatory 1, 3
• For benign concordant results from Category 3 lesions, continue mammographic follow-up every 6-12 months for 1-2 years before returning to routine screening 3

Common Pitfalls to Avoid

• Never assign Category 3 to palpable lesions - no scientific data supports this practice 2
• Never assign Category 3 based on screening examination alone - complete diagnostic workup is required first 2, 3
• Do not use Category 0 as a final assessment after complete diagnostic evaluation 2
• Avoid continuing surveillance of Category 3 lesions that demonstrate growth - these require immediate biopsy 2, 1
• Do not perform image-guided biopsy as initial evaluation for palpable masses - imaging assessment comes first 2