The underestimated risk of additional ipsilateral BI-RADS 3 lesions identified by preoperative ultrasound in breast cancer patients

OBJECTIVE: To determine the prevalence of malignancy of additional ultrasound BI-RADS category 3 lesions in women with newly diagnosed breast cancer. MATERIALS AND METHODS: Between July 2014 and June 2022, women with newly diagnosed breast cancer and additional ultrasound BI-RADS 3 lesions were retrospectively included. Malignancy was confirmed by pathology, and malignancy rates were assessed at both the patient and lesion levels. Independent risk factors for malignant BI-RADS 3 lesions were identified using multivariable logistic regression. RESULTS: A total of 1458 women (median age, 45 years; IQR: 40-51) with 1995 ultrasound BI-RADS 3 lesions were included. At the patient level, malignancy was identified in 3.5% of patients (51/1458), with higher rates for ipsilateral than contralateral BI-RADS 3 lesions (9.8% [39/397] vs 1.1% [12/1061]; p < 0.001). At the lesion level, the overall malignancy rate was 2.7% (54/1995), similarly elevated for ipsilateral compared with contralateral lesions (7.5% [41/544] vs 0.9% [13/1451]; p < 0.001). Independent predictors for malignancy of ipsilateral BI-RADS 3 lesions included same-quadrant location as the primary lesion (OR, 4.3; 95% CI: 1.9, 9.7; p < 0.001), ultrasonographic architectural distortion of the primary lesion (OR, 8.5; 95% CI: 1.6, 46.1; p = 0.01), and mammographic suspicious calcification of the primary lesion (OR, 2.9; 95% CI: 1.4, 6.0; p = 0.004). CONCLUSION: Additional ipsilateral ultrasound BI-RADS 3 lesions in women with newly diagnosed breast cancer demonstrated malignancy rates exceeding the 2% BI-RADS threshold, particularly when located in the same quadrant as the primary cancer. KEY POINTS: Question The malignancy risk of additional BI-RADS 3 lesions identified by preoperative ultrasound in breast cancer patients remains unclear. Findings Ipsilateral lesions, especially in the same quadrant, show malignancy rates exceeding 2%, while malignancy risk remains low for contralateral BI-RADS 3 lesions. Critical relevance statement Ipsilateral BI-RADS 3 lesions in the same quadrant as the primary cancer, or those with primary tumor architectural distortion or suspicious calcifications, warrant biopsy. This ensures precise surgical planning and avoids missing additional malignancy.