Anaplastic thyroid carcinoma which accounts for approximately 5% of all thyroid carcinomas is one of the most aggressive cancers, grows rapidly, develops extensive metastasis, and has a short survival. Anaplastic thyroid carcinoma may represent transformation of a well-differentiated thyroid cancer can developed from pre-existing well-differentiated thyroid carcinomas. anaplastic transformation usually is observed in primary lesions of thyroid gland. there is a few reports about anaplstic transformation occurring in metastatic lesions. we report a rare case of papillary thyroid carcinomas with anaplastic trasformation in a metastatic cervical lymph node after total thyroidectomy and radioactive iodine therapy.