The lymph nodes in the neck are abundant in the human body, so normal people will find swollen lymph nodes in the neck at one time or another. Generally, swollen lymph nodes in the neck are caused by acute and chronic inflammation of the head, mouth and throat, but in some patients, the swollen lymph nodes are related to tumor metastasis, especially thyroid cancer. Since the lymph nodes in the neck are relatively superficial, ultrasound can distinguish well between normal and abnormal lymph nodes. Generally, normal enlarged lymph nodes appear as oval-shaped on ultrasound and lymphatic portals or umbilical structures are visible. In the case of lymph nodes caused by metastatic thyroid cancer, the ultrasound may show lymph nodes that are parked, the lymphatic portal structure disappears, and punctate calcification or liquefaction in the lymph nodes. It is worth pointing out that ultrasound is more sensitive to lymph nodes metastasized around the blood vessels in the neck, but not very sensitive to lymph nodes metastasized around the thyroid gland (central group lymph nodes).