Abstract: Lymph node metastasis (LNM) in breast cancer is a key factor associated with poor prognosis in patients. Its occurrence involves a multi-stage dynamic process, including tumor cell escape, immune evasion, metabolic reprogramming, and microenvironment remodeling. In recent years, the combined application of single-cell RNA sequencing (scRNA-seq) and spatial transcriptome sequencing (ST-seq) has revealed the molecular heterogeneity between primary breast cancer lesions and metastatic lymph nodes. This review elucidates the multidimensional regulatory network of breast cancer LNM, discusses the evolution of tumor cells and their interaction with the tumor microenvironment, and emphasizes the clinical value of targeting key molecular pathways as a theoretical basis for optimizing individualized treatment strategies. Although research has preliminarily clarified the molecular mechanisms of LNMs, it remains necessary to integrate multi-omics data to construct efficient predictive models that guide personalized treatment decisions, optimize axillary lymph node management strategies, and ultimately improve the survival of patients.