What is the BI-RADS (Breast Imaging-Reporting and Data System) classification of a hypoechoic breast lesion with a macrolobulated margin, internal vasculature, and documented progression in size?

BI-RADS Classification

This lesion is BI-RADS 4 (suspicious abnormality warranting biopsy), and given the documented progression in size, it should be classified as BI-RADS 4B or 4C depending on the degree of suspicion. 1

Key Features Supporting BI-RADS 4 Classification

The combination of concerning sonographic features places this lesion firmly in the suspicious category:

• Hypoechoic appearance with macrolobulated margins are suspicious features that elevate concern beyond benign (BI-RADS 3) 2
• Internal vascularity adds to the suspicion for malignancy 2
• Documented progression in size is a critical feature that automatically upgrades any lesion to require tissue diagnosis, as growth indicates biological activity inconsistent with stable benign disease 1

Why This Cannot Be BI-RADS 3

BI-RADS 3 (probably benign) requires:

• Lesions must be less than 2 cm with low clinical suspicion 1
• Lesions must remain stable on follow-up imaging 1
• The malignancy risk must be less than 2% 3

Any lesion that increases in size on follow-up automatically requires tissue sampling and cannot remain in BI-RADS 3. 1

Subcategorization Within BI-RADS 4

The BI-RADS 4 category can be further refined:

• BI-RADS 4A (low suspicion): 10% malignancy rate 4
• BI-RADS 4B (intermediate suspicion): 21% malignancy rate 4
• BI-RADS 4C (moderate concern): 70% malignancy rate 4

Given the macrolobulated margins, internal vascularity, and documented growth, this lesion likely falls into BI-RADS 4B or 4C rather than 4A. 4, 2

Immediate Management Required

Core needle biopsy (preferred) or surgical excision with specimen radiograph is mandatory for all BI-RADS 4 lesions. 1, 3

• The overall positive predictive value for malignancy in BI-RADS 4 lesions ranges from 34% to 44.9% 5, 6
• Pathology-imaging concordance must be documented after biopsy 1, 3
• If pathology and imaging are discordant, repeat imaging and additional tissue sampling or surgical excision is required 1

Critical Pitfall to Avoid

Never observe a lesion that has demonstrated growth, regardless of other benign-appearing features. Progression in size overrides all other considerations and mandates tissue diagnosis. 1