Only one lymph node metastasis of breast cancer indicates that breast cancer has already had regional lymph node metastasis, and only a few nearby lymph nodes are involved, which refers to the situation of pN1. Breast cancer is a common malignant tumor in women, and lymph node metastasis can occur with the development of the disease, and the most common one is axillary lymph node metastasis, which can be manifested by local lymph node enlargement and pain. According to pathological examination, pN1 includes the occurrence of 1~3 lymph node metastasis. At this time, it is necessary to combine the primary tumor and whether there are distant metastases to determine the specific stage of the disease, and then decide the specific treatment and evaluate the prognosis in combination with the patient’s own situation. Lymph node metastasis of breast cancer is the result of the development of the disease, it is recommended to consult with regular hospitals in time, improve the examination under the guidance of doctors, and standardize the treatment after clarification.