Thyroid adenoma: Most patients are asymptomatic, mostly found by chance, and generally have a long course with slow development. The early manifestations are painless lumps in the anterior neck area, mostly solitary, round, oval or nodular, varying in size, with clear borders, medium hardness, smooth surface and good mobility, which can move up or down with swallowing. Because of no discomfort, it is mostly date like in size when found. Sometimes, the tumor can suddenly increase in size and be accompanied by distension and discomfort, mostly due to bleeding within the tumor capsule. Very few larger adenomas may have tracheal compression, but compression of the recurrent laryngeal nerve is extremely rare. Papillary thyroid carcinoma: It is a low-grade malignant, slow-growing tumor with no discomfort, and is diagnosed late. The tumor is mostly solitary, hard, irregular, with unclear border and poor mobility. Larger tumors are often associated with cystic changes, and light brownish-yellow liquid can be extracted by puncture, which is easily misdiagnosed as cyst; smaller ones are not easily palpable, and are often diagnosed by finding metastatic enlarged lymph nodes. In advanced stage, the tumor may invade and compress the adjacent tissues and organs, causing hoarseness, difficulty in breathing and dysphagia. This type of lymph node metastasis can occur at an early stage, and about half of the patients have metastasis at the time of initial diagnosis, while hematogenous metastasis is less common, accounting for only 4-8.6%. Follicular carcinoma of the thyroid gland: It usually occurs in middle-aged people, mostly in iodine-deficient goiter endemic areas, and some patients have a history of nodular goiter for many years. The disease usually has a long duration and grows slowly, but a few patients may show a recent increase in growth. The masses are mostly solitary, solid, hard, mobile, smooth, with indistinct borders, and often lack any indication of local malignancy. Hematogenous metastasis is common, and lymphatic metastasis occurs less frequently, and some patients can be seen with bone metastasis as the first symptom. The metastatic cancer tissue can be well differentiated and resembles the normal thyroid follicular structure and has strong iodine uptake function, so it is called “benign metastatic thyroid adenoma”. Medullary thyroid carcinoma: This type is rare, and the mass is mostly confined to one lobe of the gland, with slow growth and long course. Medullary carcinoma originates from parafollicular cells of the thyroid gland, which do not have the function of synthesizing and secreting thyroxine, but mainly secrete calcitonin, prostaglandin, 5-hydroxytryptamine and other biologically active substances, so the clinical manifestations of medullary carcinoma are very different from other types of thyroid cancer. About 30% of patients with medullary carcinoma have persistent diarrhea, which is watery and dilute, about 10 times a day, accompanied by flushing. After resection of the tumor, the diarrhea disappears, but when the metastasis recurs, the diarrhea recurs again. There are 10%-20% of patients with medullary carcinoma have family tendency and are accompanied by various endocrine diseases, such as pheochromocytoma, carcinoid syndrome, Cushing’s syndrome, etc., which are now confirmed to be orthosomal inheritance. Medullary carcinoma is predominantly lymphatic metastasis, and about 60% of patients have lymph node metastasis in the neck at the time of initial diagnosis. Undifferentiated carcinoma of the thyroid gland: It is a type of highly malignant tumors, including large cell carcinoma, small cell carcinoma, spindle cell carcinoma, squamous cell carcinoma and mucinous adenocarcinoma, etc. It is more common in elderly males. Patients with undifferentiated carcinoma usually have a history of goiter or thyroid nodules for many years. The masses suddenly increase in size recently, develop rapidly and invade adjacent tissues within a short period of time, resulting in hoarseness, choking, pain, dyspnea, dysphagia, and diffuse bilateral giant thyroid masses that are hard, fixed and not smooth when examined. The rate of metastasis to the lymph nodes in the neck is high and often prone to hematogenous metastasis.