BI-RADS

ACR Breast Imaging Reporting and Data System — final assessment category

BI-RADS category

0 — Incomplete

1 — Negative

2 — Benign

3 — Probably benign

4A — Low suspicion

4B — Moderate suspicion

4C — High suspicion

5 — Highly suggestive of malignancy

6 — Known, biopsy-proven malignancy

Evidence

Original publication

American College of Radiology. ACR BI-RADS Atlas, 5th edition. Defines the standardised final assessment categories used here (0, 1, 2, 3, 4A–4C, 5, 6) and their associated likelihood of malignancy, for mammography, breast ultrasound, and breast MRI reporting.

Guideline

Category 0 means the assessment is incomplete and calls for additional imaging or comparison with prior studies, not a result in itself. Category 3 is generally followed with a short-interval (typically 6-month) imaging follow-up rather than biopsy. Categories 4A–4C and 5 are recommended for tissue diagnosis. Category 6 is used once malignancy is already confirmed by biopsy, to track a known cancer (e.g. during neoadjuvant therapy).

Last reviewed: 2026-09

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