Metastasis of thyroid cancer to 1 lymph node needs chemotherapy if it is undifferentiated cancer, but generally does not need chemotherapy if it is differentiated cancer. Thyroid cancer is usually treated with surgery and radiation therapy, and chemotherapy is relatively ineffective. Differentiated thyroid cancer is generally preferred to be treated by surgery, and patients with good iodine uptake function are more likely to choose radionuclide treatment; while medullary carcinoma is generally chosen to be treated by radiation therapy after surgery. Undifferentiated thyroid cancer is poorly differentiated and can be treated with surgery at early stage, but due to its rapid progression, more patients have already lost the chance of surgery at the time of diagnosis, and due to poor iodine uptake function, the effect of 131 iodine radionuclide treatment is not good. Therefore, for undifferentiated thyroid cancer, radiation therapy, chemotherapy and targeted therapy become the main treatment modalities. Generally, if there is one lymph node metastasis, it belongs to stage ⅣB or ⅣC. Stage ⅣB undifferentiated thyroid cancer can be treated with chemotherapy on the basis of radiotherapy, and stage ⅣC can be considered to be treated with systemic chemotherapy. If thyroid cancer is differentiated or medullary carcinoma, chemotherapy is usually not needed. Patients are advised to consult with specialists for comprehensive judgment based on the pathological type of thyroid cancer, size of lesions, distant metastasis, etc., and follow the doctor’s instructions for treatment.