Anaplastic Thyroid Carcinoma Following Radioactive Iodine Therapy for Graves ’ Disease

Radioactive iodine (RAI) therapy has been used as a treatment option for Graves ’ disease, and it has been widely accepted to be safe. On the other hand, some evidence suggests that RAI therapy is possibly associated with a small increased risk of thyroid cancer. Herein, we report a rare case of anaplastic thyroid carcinoma (ATC) associated with Graves ’ disease, following RAI treat-ment. A 42-year-old woman had been diagnosed with Graves ’ disease and although she was treated with an antithyroid drug, she remained in a hyperthyroid state, which led to two RAI treatments. More than 10 years later, the patient revisited our clinic due to hoarseness, dysphagia, and dyspnea, which had lasted for 2 months. Neck computed tomography suggested thyroid carcinoma and a lymph node biopsy showed metastatic papillary carcinoma. The patient underwent total thyroidectomy and was finally di-agnosed as having an ATC. It is not clear if the occurrence of ATC reported here was influenced by the RAI therapy or alterna-tively, it may only represent the delayed recognition of a rare change in the natural history of Graves ’ disease. Nevertheless, this report is worthwhile since it presents a very rare case of ATC that occurred eleven years after the RAI therapy for Graves ’ disease