Histologic Findings and Cytological Alterations in Thyroid Nodules After Radioactive Iodine Treatment for Graves' Disease: A Diagnostic Dilemma.

Unlike the well-documented relation between radiation to the neck and development of papillary thyroid carcinoma, a causal association between radioactive iodine treatment for Graves' disease and development of thyroid malignancy is less defined. However, patients with a background of thyroid dysfunction presenting with clinically palpable thyroid nodules are followed more closely than the average population, and fine needle aspiration is recommended in such circumstances. Cytological examination of aspirates, and histologic examination of tissue provided from patients with a known history of Graves' disease, managed by radioactive iodine therapy can create a diagnostic dilemma, as the distinction between radiation effect and a malignant primary thyroid neoplasm can be very challenging. Thus, pathologists should be aware of the existence of these changes in the setting of radiation therapy for Graves' disease. Providing pathologists with appropriate clinical history of Graves' disease treated with radioactive iodine is of paramount importance in order to prevent an overdiagnosis of malignancy.