Anaplastic carcinoma - Seen in 7th-8th decade -C/F Sudden increase in the size of swelling Severe pain over the swelling Most common route of spread- Direct invasion Evidence of compression of Trachea - Dyspnea Esophagus - Dysphagia Recurrent laryngeal nerve - Hoarseness of voice Most common site of metastasis - Lungs - Investigations IOC for Diagnosis- FNAC - Treatment For resectable tumor - Total thyroidectomy For unresectable tumor - Tracheostomy (lifesaving procedure when tumor is obstructing trachea) - Poor prognosis.