Chemotherapy is not mandatory after breast cancer surgery. Doctors need to decide whether chemotherapy is needed based on the patient’s tumor stage, risk of recurrence, and type of tumor pathology. For in situ breast cancer patients, chemotherapy is generally not advocated. However, for those with positive axillary lymph nodes and high risk of recurrence factors, it is appropriate to apply postoperative adjuvant chemotherapy. Breast cancer is one of the solid tumors with high effective rate of applying chemotherapy, therefore, chemotherapy has an important position in the whole treatment of breast cancer, including preoperative chemotherapy, postoperative adjuvant chemotherapy, palliative chemotherapy and so on. Through surgery doctors can help patients remove the tumor load as much as possible. For patients with in situ breast cancer, postoperative adjuvant chemotherapy is generally not advocated, but for those with positive axillary lymph nodes and high risk of recurrence factors, it is appropriate to apply postoperative adjuvant chemotherapy or radiotherapy, endocrine therapy, etc. to reduce the risk of recurrence and metastasis. Whether postoperative chemotherapy for breast cancer needs to be judged comprehensively under the guidance of professional doctors according to the pathology and staging, etc. It is recommended that patients should seek emergency treatment in time and actively cooperate with the treatment so as not to delay the condition.