BI-RADS Edition History
| Edition | Year | Key Changes |
|---|---|---|
| 1st | 1993 | Mammography only; established categories 0–5 |
| 2nd | 1995 | Refined mammography lexicon; added follow-up guidance |
| 3rd | 1998 | Expanded lexicon; introduced audit requirements |
| 4th | 2003 | Added US and MRI lexicons; introduced 4A/4B/4C subcategories |
| 5th | 2013 | Unified lexicon across all three modalities; revised density categories A–D; refined malignancy risk thresholds per subcategory; added Category 6 (known malignancy); standardized NME terminology for MRI |
BI-RADS Assessment Categories
| Category | Label | Malignancy Risk | Management Action |
|---|---|---|---|
| 0 | Incomplete — Need Additional Imaging | N/A | Recall for additional imaging and/or comparison to prior studies |
| 1 | Negative | Essentially 0% | Routine screening interval |
| 2 | Benign | Essentially 0% | Routine screening interval |
| 3 | Probably Benign | ≤2% | Short-interval follow-up: 6 months → 12 months → 24 months → return to annual |
| 4A | Suspicious — Low | >2–10% | Tissue sampling recommended |
| 4B | Suspicious — Intermediate | >10–50% | Tissue sampling; radiologic-pathologic concordance critical |
| 4C | Suspicious — High | >50–95% | Tissue sampling; benign pathology requires concordance review |
| 5 | Highly Suggestive of Malignancy | ≥95% | Biopsy required; neoadjuvant planning may proceed concurrently |
| 6 | Known Biopsy-Proven Malignancy | N/A | Awaiting treatment; used for monitoring prior to surgery |
Category 0 is a screening-only category. Never assign BI-RADS 0 on a diagnostic workup unless prior comparison films are truly unavailable. BI-RADS 3 is a diagnostic category — do NOT assign it on a screening study; assign 0 and complete the diagnostic workup first.
Category 3 — Probably Benign: When to Use
BI-RADS 3 applies to findings with ≤2% malignancy risk that have well-established benign imaging criteria:
- Mammography: Oval circumscribed non-calcified mass; focal asymmetry without other suspicious features
- Ultrasound: Oval circumscribed solid mass (parallel orientation, no suspicious features); complicated cyst; clustered microcysts
- MRI: Oval/round circumscribed mass with persistent kinetics and dark internal septations
BI-RADS 3 caveats — consider biopsy instead of surveillance if: patient is pregnant or lactating with a new mass · newly diagnosed with cancer elsewhere · elevated risk (≥20% lifetime) · unreliable for follow-up · strong patient preference for tissue diagnosis.
Category 4 Subcategories
Subcategorizing 4A/4B/4C is optional for mammography and US but strongly recommended for MRI, where it significantly impacts post-biopsy management:
- 4A: Low suspicion — benign biopsy result is accepted if concordant; no further workup needed
- 4B: Intermediate — concordance review required; discordant benign pathology needs repeat biopsy
- 4C: High — benign pathology is almost always discordant; repeat biopsy or surgical excision required
After BI-RADS 4C or 5: A benign biopsy result is almost always discordant. Radiologic-pathologic concordance review is mandatory. Repeat biopsy or surgical excision is typically required.