A swollen lump on the left side of the neck is considered more likely to be a thyroid disorder. The most common is simple thyroid adenoma, which manifests as a localized elevated swelling, especially when swallowing, and there will be obvious discomfort or pain. The gradual enlargement of the tumor may also compress the trachea, manifesting as a feeling of pressure, accompanied by chest tightness or restricted breathing. The cause of thyroid adenoma is related to the compensatory hyperplasia of the gland, and it is considered to be related to the abnormal metabolism of thyroxine in the body, and in serious cases, surgical treatment is needed to remove the lesion. In some patients, it is caused by the enlargement of lymph nodes in the neck, which may be manifested as a localized mass, which can be seen in local soft tissue infection or malignant tumors with metastasis to the lymph nodes in the neck. The investigation will be manifested as a localized hard mass, accompanied by swelling and pain, if necessary, but also need to choose surgery for excision biopsy, clear pathology to guide the next step in the treatment.