FINE-NEEDLE ASPIRATION BIOPSY OF THE THYROID-GLAND IN PATIENTS WITH PRIOR GRAVES-DISEASE TREATED WITH RADIOACTIVE IODINE - MORPHOLOGIC FINDINGS AND POTENTIAL PITFALLS

OBJECTIVE: To evaluate the morphologic findings and their potential pi tfalls in fine needle aspiration biopsies (FNAB) of thyroid glands obt ained following radioactive iodine (RaI) (131I) treatment for Graves' disease. STUDY DESIGN: Study of thyroid FNAB specimens from six patien ts with prior Graves' disease treated with RaI who developed palpable nodules and had subsequent thyroid resections. RESULTS: The cytologic changes attributed to radiation were quite variable among the six case s and were so pronounced in one case that a false positive diagnosis o f papillary carcinoma was made even though a history of RaI had been p rovided. The FNAB specimen from the second case, submitted without a h istory of RaI treatment, was diagnosed as suspicious for papillary car cinoma. The smears from patient 3 were signed out descriptively becaus e the pertinent clinical history had not been provided. The FNAB speci mens from the last three patients were correctly interpreted because o f the history of RaI therapy provided. All six thyroid surgical specim ens showed changes consistent with radiation injury, and none containe d evidence of malignancy. CONCLUSION: The study's findings demonstrate that the atypia produced by RaI may be severe, leading to an erroneou s diagnosis of malignancy. Provision of the appropriate clinical histo ry of Graves' disease treated with RaI may prevent this pitfall.