Thyroid cysts are one of the most common benign masses found in the thyroid gland. Generally, they do not become cancerous and usually have no clinical symptoms; therefore, thyroid cysts themselves do not cause fever. If a patient with a thyroid cyst develops a fever, it is important to consider whether there might be a concurrent infectious disease. If there is pain in the area of the thyroid, it is necessary to evaluate for conditions such as thyroiditis or a thyroid abscess. A simple thyroid cyst alone would not cause a fever.