Nodal positivity in breast cancer correlated with the number of lesions detected by magnetic resonance imaging versus mammogram

Background: Magnetic resonance imaging (MRI) in breast cancer can detect more than 15% additional lesions than mammography. We investigated lymph node metastases rates in patients with multifocal or multicentric disease detected by MRI compared with patients with a single lesion detected by mammography and magnetic resonance imaging. Methods: A retrospective analysis of breast cancer patients undergoing MRI and mammography was performed. The objective was to compare lymph node metastases rates in patients with additional lesions detected by MRI versus a single lesion detected by mammography or MRI. Results: Of 413 patients, 318 were included for the study. The overall nodal metastases rate was 24.8%. MRI detected multiple lesions in 83 (26.1%) patients; 67 (21.1%) patient MRI findings were not detected by mammography. The lymph node metastases rate was 37.3% when <2 lesions were detected compared with 20.2% when a single malignant lesion was detected (P = .01). The evaluation of the 67 patients with additional lesions detected by MRI revealed 32 patients with invasive lesions, 29 with benign lesions, and 6 with in situ disease. Comparing patients with single malignant lesions with patients with additional malignant lesions detected by MRI, the lymph node metastases rate increased from 20.2% to 50% (P = .002). Conclusions: Our study shows a significant increase in the lymph node metastases rate in patients with additional malignant lesions detected by MRI. This finding suggests that MRI-detected malignant lesions are biologically significant and may predict more aggressive disease.