Management of metastasis to the thyroid gland.

We present 4 cases with metastasis to the thyroid gland (MTG), and discussed the diagnosis and treatment of MTG. It is not always easy to correctly diagnose MTG from primary thyroid cancer. Although fine needle aspiration biopsy is useful for the diagnosis of MTG, it is important to take other imaging studies and/or tumor marker into consideration. Thyroidectomy for MTG is controversial, but the good indication of thyroidectomy is considered for the patient whose primary tumor is controllable. Thyroidectomy may also be useful even for the patient with uncontrollable disease to prevent respiratory and swallowing problems caused by MTG.