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Thyroid carcinoma is a slowly growing tumor and rarely invades adjacent tissues or organs. However, up to 21% of the patients with well－differentiated thyroid cancers show local invasion, and of those 10 to 15% of patients with papillary cancer who eventually die of the disease, active local disease has been the most common finding at the time of death. The common sites of local invasion are strap muscle, recurrent laryngeal nerve, laryngotracheal tree, esophagus, and great vessels in the lateral compartment and mediastinum. Uncontrolled local invasion to vital organs in the neck causes significant morbidity, affects the quality of life, and finally influences the survival. In cases with limited involvement of the larynx or trachea, the option of treatment includes limited shaving－off resection or radical resection followed by reconstructive procedures. When operation is planned, the level of acceptable morbidity and the achievement of therapeutic outcomes should be determined in advance. In cases with aggressive invasion to the adjacent tissues, radical resection is the treatment modality of choice with favorable prognosis. Postoperative adjuvant therapies have been the matter of controversy, however, there is a general consensus, especially for the high－risk patients, that radioiodine therapy and TSH suppression after radical resection are beneficial. The benefits of external radiation therapy in locally advanced thyroid cancers are unclear, however, it can be effective in patients with microscopic residual disease postoperatively. Radical eradication of locally advanced thyroid carcinoma followed by appropriate adjuvant therapy should be considered to be the treatment of choice in locally advanced thyroid cancers.
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