Thyroid cancer stage 4a belongs to the stage of ultrasound examination, which is used to indicate the degree of malignancy of the tumor, and has no great relationship with how many years the patient can live. Stage 4a thyroid cancer means that the diagnosis of thyroid cancer has been confirmed, and the cancer has exceeded the thyroid peritoneum and invaded the subcutaneous soft tissues, larynx, trachea, esophagus or laryngeal recurrent nerves, which belongs to the middle and advanced stage. Surgical resection and lymph node dissection are the main treatment options, and iodine 131 therapy and levothyroxine tablet replacement therapy should also be given after surgery. How many years can thyroid cancer 4a live is mainly related to the tumor’s pathology, differentiation and clinical staging. Clinically, 5-year survival rate is commonly used to determine how long patients can live. If it is follicular or papillary thyroid cancer with low malignancy, the 5-year survival rate of mid-stage thyroid cancer can reach 98% after systematic treatment; the 5-year survival rate of advanced thyroid cancer can reach about 90%. And if it is medullary or undifferentiated cancer, the 5-year survival rate of grade 4a is very low, below 10%. Therefore, the thyroid condition should be checked regularly.