ABSTRACT
Thyroid insular carcinoma (TIC, poorly differentiated thyroid carcinoma) is derived from thyroid follicular cells and known to show pathophysiologic behaviors intermediate between well-differentiated and undifferentiated types of thyroid carcinoma. The estimated incidence of TIC is from 0.4% to 5% of all thyroid cancers and is rare in Asians. Moreover, the multiple bone metastases in TIC have been rarely reported so far. Clinically, there are two pathways that thyroid cancer is presented, either as a parapharyngeal or retropharyngeal mass. For the first pathway, the mass is located on the thyroid upper pole and it grows toward the anatomical defect of posterior aspect of inferior pharyngeal constrictor. The second pathway involves a pharynx directly compressed by the mass from outside to inside of inferior pharyngeal constrictor. A 66-year-old man who had a thyroid mass revealed important clinical findings: a right pyriform sinus mass from laryngoscopy and multiple bone metastases from radiology. We performed subtotal thyroidectomy with central neck dissection. The mass was confirmed as TIC from follicular thyroid carcinoma. The patient received radiation and radioactive iodine therapy, and bcause of a remnant thyroid mass, he was observed closely. We herein report a rare, unique case of TIC with a review of literatures.