Thyroid cancer invading the recurrent laryngeal nerve needs to be treated by surgery or chemotherapy, depending on the condition. Surgery is the first choice. If only the recurrent laryngeal nerve is invaded and there is no hoarseness, the nerve can be separated and the lesion can be removed during surgery. Undifferentiated thyroid cancer may need chemotherapy after surgery, and differentiated thyroid cancer is usually treated with iodine 131 after surgery if it is not cleanly cut. If it has affected the surrounding tissues and gone deeper, the nerves need to be removed or a total thyroidectomy with lymph node dissection is performed. Preoperative chemotherapy is needed to shrink the cancer before surgery, and chemotherapy drugs will continue to be used after surgery. Thyroid cancer that invades the recurrent laryngeal nerve can cause hoarseness, and if both sides are invaded, it can also cause choking. Therefore, once thyroid cancer is detected, it must be treated promptly.