Utilizing MRI to Downgrade suspicious Breast Lesions Detected on Ultrasound: How often Can Unnecessary Breast Biopsies be Avoided?

Abstract Background Breast cancer remains the most frequently diagnosed malignancy and the primary cause of cancer-related death among women globally. As per the BI-RADS atlas, category 4 lesions generally require histopathological assessment through biopsy rather than follow-up imaging. Nevertheless, many lesions initially classified as BI-RADS 4A and 4B on ultrasound are subsequently found to be benign. This contributes to a high rate of unnecessary biopsies, increasing healthcare costs and significant psychological burden for patients. Magnetic resonance imaging, especially when combined with diffusion-weighted imaging, provides high sensitivity and a strong negative predictive value for detecting breast cancer, serving as an effective tool for assessing indeterminate or suspicious lesions. This study included 150 patients with a total of 172 breast lesions initially categorized as BI-RADS 4A or 4B based on ultrasound findings. All patients underwent contrast-enhanced MRI combined with DWI. Final diagnoses were confirmed by histopathology or by imaging follow-up over a period of at least 12 months, which served as the reference standard. The primary objective was to assess the diagnostic performance of MRI—specifically the combination of contrast-enhanced imaging and DWI—in re-evaluating ultrasound-suspicious lesions. The aim was to accurately downgrade benign lesions, thereby reducing unnecessary biopsies, improving diagnostic accuracy, and supporting more informed clinical decision-making. Results Among the 172 lesions (130 BI-RADS 4A and 42 BI-RADS 4B), 61 (35.5%) were malignant. MRI accurately identified all malignant lesions and correctly diagnosed 103 out of 111 benign lesions (92.8%). MRI increased the positive predictive value from 35.5% (61/172) to 88.4% (61/69) and reduced false-positive ultrasound findings—those leading to unnecessary biopsies—by 92.8%. MRI also downgraded 103 lesions (59.9%) to lower BI-RADS categories. The combined protocol achieved 100% sensitivity, 92.8% specificity, 88.4% PPV, 100% NPV, and 95.3% overall accuracy. Additionally, MRI identified five suspicious lesions (2.9%) not visualized on ultrasound, four of which were malignant. Conclusions MRI demonstrates robust efficacy in downgrading BI-RADS 4A and 4B lesions identified on ultrasound, significantly reducing unnecessary biopsies and mitigating patient anxiety and psychological burden, while ensuring complete detection of malignant lesions. However, its high sensitivity may reveal additional suspicious findings that warrant further evaluation.