Autonomously functioning thyroid nodule treated with radioactive iodine and later diagnosed as papillary thyroid cancer.

UNLABELLED The malignancy risk is low in hot thyroid nodules verified by scintigraphy. We present a rare case of papillary carcinoma, initially treated as an autonomous hot nodule. Case report. A 36-year old male patient with a hot thyroid nodule and subclinical hyperthyroidism was treated with 10mCi 131 I. On admission, both 99mTc and 131 I thyroid scintigraphic imaging revealed a hot nodule at the right lobe accompanied by lower uptake in the remaining thyroid tissue. After treatment, there was a progressive increase in the nodule size; a fine needle aspiration biopsy was thus performed which showed findings compatible with papillary thyroid cancer. The patient was referred to our department for further management. Total thyroidectomy with right central neck dissection was performed. The pathologic examination showed that the whole nodule (1.5 cm diameter) was a columnary type papillary thyroid cancer. CONCLUSION In the case of a small-sized toxic thyroid nodule, the possibility of malignancy cannot be totally ruled out. Suspicious hot nodules should be cytologically evaluated before radioactive iodine treatment to determine the existing malignancy risk. Fine needle aspiration biopsy should be performed in all hot thyroid nodules that increase in size after radioactive iodine treatment.