Magnetic resonance imaging for diagnosing residual malignancy after excisional biopsy for breast cancer: Comparison with excisional biopsy margin status.

Purpose: To evaluate the diagnostic performance of dynamic contrast-enhanced breast MRI and to compare it with excisional biopsy margin status in predicting residual malignancy after excisional biopsy for breast cancer. Materials: This retrospective study included 170 patients who underwent excisional biopsy followed by subsequent definitive surgery between February 2020 and October 2023. Clinical and MRI features were compared between patients with and without residual malignancy. Multivariate logistic regression was performed to identify independent predictors of residual malignancy. Diagnostic performance was assessed for MRI findings, MRI final assessment, and excisional biopsy margin status. Results: Residual malignancy was present in 88/170 patients (51.8%). Larger tumor size, positive excisional biopsy margins, and MRI final assessment suggestive of residual malignancy were significantly more frequent in the residual malignancy group (P ≤ 0.001). On multivariate analysis, positive excisional biopsy margins (OR: 2.753; P = 0.005) and MRI final assessment suggestive of residual malignancy (OR: 2.538; P = 0.009) were independently associated with residual malignancy. MRI final assessment showed lower sensitivity but higher specificity than excisional biopsy margin status (67.0% vs 73.9% and 62.2% vs 53.7%, respectively), without significant differences (P = 0.377 and 0.324). Combining both parameters improved sensitivity to 88.6% when either test was positive, and specificity to 80.5% when both tests were positive. Conclusion: MRI final assessment demonstrated diagnostic performance comparable to excisional biopsy margin. Their combined use may optimize diagnostic strategy according to clinical context, and MRI may provide complementary information, particularly when margin information is unavailable.