“Breast cancer is a common malignant tumor in women, and its lymph node metastasis is an important prognostic indicator. In recent years, the application of high-throughput technology has revealed the heterogeneity of immune cells in the tumor microenvironment of breast cancer and its key role in lymph node metastasis. Experts reviewed the dynamic changes of immune cell subsets and their regulatory mechanisms in the process of lymph node metastasis of breast cancer, providing a theoretical basis and a new perspective for achieving accurate diagnosis and individualized treatment of breast cancer in the future.”