Whether or not a thyroid cyst of 5mm is serious depends on the patient’s cyst occupancy, whether or not it is causing pressure symptoms, and whether it is benign or malignant. If there are compression symptoms or malignancy is suspected, it may be more serious. Thyroid cysts are a common thyroid disease, which is usually caused by colloid changes in thyroid nodules or adenomas, degenerative lesions, or hemorrhage in adenomas. A 5mm thyroid cyst can be treated without special treatment if it does not cause discomfort or malignancy, and only needs to be followed up to keep a close eye on the change of the cyst, which is generally not serious. If a 5mm thyroid cyst develops malignant lesions, or the cyst lesion compresses the surrounding tissues and organs, causing symptoms such as shortness of breath and difficulty in swallowing, which affects the patient’s daily life, then the patient needs to undergo surgical treatments such as thyroid cyst removal or thyroidectomy to remove the thyroid cyst. Therefore, thyroid cysts 5mm should go to the hospital in time, under the advice and guidance of the doctor to carry out regular treatment.