Morphologic and Diffusion-weighted MRI Characteristics of Axillary Lymph Nodes for Predicting Metastasis in Breast...

Accurate preoperative assessment of axillary lymph node metastasis is essential for treatment planning in breast cancer patients. This study aimed to evaluate the diagnostic performance of quantitative MRI parameters, including lymph node morphology and diffusion-weighted imagingderived Apparent Diffusion Coefficient (ADC) values, in predicting axillary lymph node metastasis.

This retrospective study included 216 female patients with histopathologically confirmed breast cancer who underwent preoperative breast MRI. Lymph node long and short axis diameters, cortical thickness, ADC values, and derived ratios were measured. Receiver Operating Characteristic (ROC) analysis and multivariate logistic regression were performed to identify independent predictors of lymph node metastasis.

Metastatic lymph nodes demonstrated significantly greater cortical thickness and lower ADC values compared with non-metastatic nodes (p < 0.001). Among all parameters, the ADC/cortical thickness ratio showed the highest diagnostic performance (AUC = 0.978; 95% CI: 0.959-0.997), with 96.2% sensitivity and 92.8% specificity. The ADC/cortical thickness ratio successfully detected 128 out of 133 metastatic lymph nodes and 77 out of 83 non-metastatic lymph nodes, with total accuracies of 96.2% and 92.8%, respectively. The test demonstrated a positive predictive value of 95.5% and a negative predictive value of 94.2%. Cortical thickness (>3.5 mm), ADC value (≤900 ×10^-3 mm²/s), and Ki-67 index (≥20%) were identified as independent predictors of lymph node metastasis.

The present study demonstrates that lymph node ADC values and ADC-based ratios provide significant diagnostic performance in differentiating metastatic from non-metastatic axillary lymph nodes. The identified cut-off values yielded clinically meaningful sensitivity and specificity, supporting the role of diffusion-weighted imaging as a non-invasive adjunct tool in preoperative axillary evaluation. These findings may contribute to improved patient stratification and may help reduce unnecessary invasive procedures in selected cases.

Quantitative MRI parameters combining morphologic and diffusion features demonstrate high diagnostic accuracy for predicting axillary lymph node metastasis in breast cancer patients. The ADC/cortical thickness ratio is a simple, reproducible imaging biomarker that may support preoperative axillary evaluation and clinical decision-making in routine breast MRI practice.