On breast ultrasound, a hypoechoic mass with an irregular shape, angular margins, and posterior acoustic shadowing is observed. According to BI-RADS ultrasound lexicon, this lesion would most appropriately be categorized as:
- A BI-RADS 2 (Benign)
- B BI-RADS 4C (High Suspicion) ✓
- C BI-RADS 3 (Probably Benign)
- D BI-RADS 4B (Moderate Suspicion)
Correct answer: B. BI-RADS 4C (High Suspicion)
Explanation
On ultrasound BI-RADS, features of malignancy include irregular shape, non-parallel orientation (taller than wide), angular or spiculated margins, heterogeneous echotexture, posterior shadowing, and duct extension. Irregular shape + angular margins + posterior shadowing is a high-suspicion combination corresponding to BI-RADS 4C (PPV 50–94%) or BI-RADS 5 if the combination is classic. BI-RADS 3 is reserved for oval, parallel, circumscribed lesions like fibroadenomas. BI-RADS 2 lesions are definitively benign (simple cysts, lipomas).
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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