A thyroid adenoma is an adenoma of the thyroid gland, which is a type of thyroid nodule and a benign thyroid swelling. The causes of adenoma formation are numerous and the mechanism is not clear. It is thought to be related to some environmental, dietary, and genetic factors. Larger adenomas can also be malignant and, most importantly, can lead to a diffuse goiter. This enlargement can have some compression symptoms, pressing on important nerves, blood vessels or the surrounding trachea and esophagus, causing difficulty in breathing, swallowing and hoarseness. Adenomas of the thyroid gland can be surgically removed. For smaller adenomas, simple adenoma removal can be performed. If the tumor is large, the gland may be removed, such as a unilateral lobectomy or a subtotal thyroidectomy.