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BI-RADS: lexicon and assessment in mammography and breast ultrasound

BI-RADS describes a finding in a uniform language (shape, margins, calcifications, distribution) and ends with a category that dictates a recommendation: 1–2 routine, 3 short-interval follow-up, 4–5 biopsy, 0 further work-up, 6 proven malignancy.

לקריאה בעברית

Why it matters in the exam

Categories: 0 — incomplete, further work-up needed; 1 — negative; 2 — benign; 3 — probably benign (malignancy risk 2% or less) — follow-up at 6 months; 4 — suspicious (4A 2–10%, 4B 10–50%, 4C 50–95%) — biopsy; 5 — highly suggestive (95% or more) — biopsy; 6 — biopsy-proven malignancy. BI-RADS 3 suits only defined findings on a baseline examination: a non-calcified circumscribed mass, a focal asymmetry, and a group of round calcifications. On US an oval, circumscribed, parallel, hypoechoic mass — BI-RADS 3.

Mass: shape (oval, round, irregular), margins (circumscribed, obscured, microlobulated, indistinct, spiculated) and density. Irregular shape and spiculated margins — the most suspicious. Architectural distortion without previous surgery — BI-RADS 4 and biopsy. Asymmetries: asymmetry (seen on one view), focal asymmetry (on two views, less than a quadrant), global (a quadrant or more, usually a normal variant), and developing asymmetry (new or enlarging — suspicious). Hamartoma ("breast within a breast"), radiolucent lipoma, intramammary lymph node and simple cyst — BI-RADS 2.

Calcifications: typically benign — skin, vascular, coarse "popcorn" (involuting fibroadenoma), large rod-like (secretory, duct ectasia), round, rim (lucent-centred), dystrophic (after surgery or radiation), "milk of calcium" (teacup on the lateral view) and sutures. Suspicious morphology: amorphous, coarse heterogeneous, fine pleomorphic and fine linear or branching (the most suspicious). Suspicious distribution: linear and segmental. A suspicious axillary lymph node on US: cortex thickened above 3 mm or eccentric, loss of the fatty hilum and a round shape. A mass in the male breast: subareolar gynaecomastia versus an eccentric mass (suspicious for cancer).

Key points

0 work-up, 1–2 routine, 3 follow-up, 4–5 biopsy, 6 proven.
BI-RADS 3 — 2% or less, 6-month follow-up.
Irregular shape and spiculation — suspicious.
Fine linear-branching and segmental — the most suspicious.
Architectural distortion without surgery — biopsy.

Summary table

Category	Meaning	Malignancy risk	Recommendation
0	Incomplete	—	Extra views or US
2	Benign	Essentially zero	Routine screening
3	Probably benign	2% or less	Follow-up at 6 months
4 (A, B, C)	Suspicious	Above 2% and below 95%	Biopsy
5	Highly suggestive	95% or more	Biopsy

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Sources

ACR BI-RADS Atlas, 5th edition (2013) — Mammography, ultrasound and MRI lexicons; Assessment categories
ACR Appropriateness Criteria: Palpable Breast Masses, 2022 — Initial imaging by age

Sources are given for further reading; the text is written afresh and not copied from them.

Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.