Anatomical Variations of Axillary Lymph Nodes Affect the Accuracy of Preoperative Breast MRI Nodal Staging

Objective: To determine whether anatomical nodal distribution patterns of axillary lymph nodes influence the accuracy of breast magnetic resonance imaging (MRI) nodal staging in patients with breast cancer. Methods: This retrospective study included 156 consecutive patients with newly diagnosed breast cancer who underwent contrast-enhanced breast MRI followed by histopathological nodal evaluation. Two experienced breast radiologists, blinded to pathology results, independently reviewed all MRI examinations. The axillary nodal distribution pattern, the presence of interpectoral (Rotter) lymph nodes, the presence of internal mammary lymph nodes, and the clustered nodal pattern were recorded. MRI-based clinical nodal staging was compared with histopathological nodal status. Multivariable logistic regression identified independent predictors of false-negative MRI nodal staging. Results: Histopathological nodal metastases were identified in 58 patients (37.2%). Breast MRI demonstrated a sensitivity of 70.7% [95% confidence interval (CI), 57.3-81.9%] and a specificity of 84.7% (95% CI, 76.0-91.2%) for detecting nodal metastases. False-negative MRI staging was significantly more frequent among patients with a level II/III-dominant nodal distribution than among those with a level I-dominant pattern (33.3% vs. 25%, P=0.02). Patients with interpectoral (Rotter) lymph nodes had a higher false-negative rate than patients without Rotter lymph nodes (50% vs. 20%, P=0.01). Both a level II/III-dominant nodal distribution [adjusted odds ratio (OR), 2.6; 95% CI, 1.1-6.4] and the presence of interpectoral (Rotter) lymph nodes (adjusted OR, 2.9; 95% CI, 1.2-7.1) independently predicted false-negative MRI nodal staging. Conclusion: Anatomical distribution patterns of axillary lymph nodes influence the accuracy of MRI nodal staging. Assessing nodal distribution, particularly a level II/III-dominant pattern and interpectoral (Rotter) lymph nodes, may improve nodal evaluation and reduce false-negative rates in MRI staging. © 2026 The Author(s). Published by Galenos Publishing House on behalf of the Turkish Society of Magnetic Resonance.