[Anaplastic thyroid carcinoma developed after treatment of "hot" thyroid nodule with radioiodine]

A case of 55 years old woman with "hot" right lobe toxic thyroid nodule, presenting with paroxysmal atrial fibrillation, and therefore treated with 131I 666MBq (18 mCi) is described. After six years she became pyrexic and suffered of severe cough proxyisms. The fine needle biopsy of the above nodule showed the presence of anaplastic thyroid carcinoma. Strumectomy followed by local radiotherapy resulted in complete disappearence of all symptoms. The microscopic of the removed thyroid tissue confirmed the above diagnosis. After 22 months' observation the patient remained in good general condition. The possible reasons for the development of the thyroid carcinoma in this case are discussed.