For well-differentiated thyroid cancers (papillary and follicular carcinoma), follow-up should include: • Periodic physical examination, especially of the thyroid and cervical lymph nodes . • Serologic marker (thyroglobulin). • Scanning with radioactive iodine and treatment with 30 MCi (millicuries) (low-risk patients) or 100 MCi (high-risk patients if they have had a total or near-total thyroidectomy). • Periodic ultrasound examinations of the neck to identify recurrence in the thyroid area or lymph node metastases. • Chest x-ray to detect metastases. For medullary thyroid cancer, follow-up should include: • Serum calcitonin level and CEA level every six months. • Physical examination, emphasizing the thyroid, although calcitonin level is more accurate than physical examination for following persistent disease. • CT or MRI scan of neck and mediastinum . • Chest x-ray every six months until stable. • Chemistry panel every six months.