Pain on the left side of the neck when swallowing is not necessarily cancer, but may be caused by inflammation of the throat or lymph nodes in the neck, or inflammation of the thyroid gland. At this time, you can go to the ENT department to do a checkup of the throat, and do ultrasound of the lymph nodes in the neck to see if there is lymph node inflammation and ultrasound of the thyroid gland to see if there is inflammation of the thyroid gland, etc. If it is confirmed to be inflammation, give anti-inflammatory treatment to reduce or disappear, then it means that it is caused by this aspect. If inflammation is confirmed and anti-inflammatory treatment is given, and the pain is reduced or disappears, it means that it is caused by this aspect. If all the above reasons are ruled out and the pain does not subside after anti-inflammatory treatment, it is necessary to do the appropriate examination as soon as possible to rule out whether it is caused by malignant diseases in the larynx or esophagus. Although the possibility is relatively very small, it is still necessary to pay attention to it and have it examined at the earliest possible time.