This study aims to evaluate whether longitudinal multimodal ultrasound can accurately predict axillary pathological response in breast cancer patients who receive neoadjuvant chemotherapy. In this study, patients with biopsy-proven metastatic axillary lymph nodes will have a metallic clip placed in the positive node before chemotherapy. During and after treatment, the clipped lymph node will be monitored by ultrasound, including gray-scale imaging, shear wave elastography, and contrast-enhanced ultrasound. The changes in the morphological and functional features of the clipped node will be analyzed to establish a predictive model for axillary pathological complete response. The results are expected to help identify patients who may safely avoid unnecessary axillary lymph node dissection and improve individualized surgical decision-making.