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BI-RADS (Breast Imaging Reporting and Data System) is a standardized reporting framework developed by the American College of Radiology (ACR) to ensure consistent terminology, assessment structure, and management recommendations in breast imaging (mammography, ultrasound, MRI).
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| Category | Meaning | Likelihood of Malignancy | Management |
|---|---|---|---|
| 0 | Incomplete | - | Needs additional imaging |
| 1 | Negative | 0% | Routine screening (annual) |
| 2 | Benign finding | 0% | Routine screening |
| 3 | Probably benign | <2% | Short-interval (6-month) follow-up |
| 4 | Suspicious abnormality | 2–95% | Biopsy recommended |
| 4A | Low suspicion | 2–10% | Biopsy recommended |
| 4B | Moderate suspicion | 10–50% | Biopsy recommended |
| 4C | High suspicion | 50–95% | Biopsy recommended |
| 5 | Highly suggestive of malignancy | >95% | Appropriate action (e.g. surgery) |
| 6 | Known biopsy-proven malignancy | 100% | Treatment planning |
Descriptors by Modality:
| Modality | Utility | Descriptor |
|---|---|---|
| Mammography | Screening and diagnosis; assess calcifications, masses | • Mass: Shape (round, oval, irregular), margin (circumscribed, microlobulated, obscured, indistinct, spiculated), density |
| • Calcifications: Benign vs suspicious (amorphous, coarse, fine pleomorphic) | ||
| • Asymmetries: Focal, developing, global | ||
| • Architectural distortion | ||
| Ultrasound | Characterize palpable masses; adjunct to mammography | • Mass: Shape, orientation (parallel or not), margin, echo pattern, posterior features |
| • Associated features: Skin thickening, duct changes, axillary adenopathy | ||
| MR | High-risk screening, staging, treatment response | • Mass: Shape, margin, internal enhancement pattern |
| • Non-mass enhancement: Distribution (focal, linear, segmental), internal enhancement | ||
| • Kinetics: Initial enhancement and delayed phase (washout, plateau, persistent) |
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BI-RADS lexicon: