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 pitfalls in fine needle aspiration biopsies (FNAB) of thyroid glands obtained following radioactive iodine (RaI) (131I) treatment for Graves' disease.

STUDY DESIGN

Study of thyroid FNAB specimens from six patients 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 cases and were so pronounced in one case that a false positive diagnosis of papillary carcinoma was made even though a history of RaI had been provided. The FNAB specimen from the second case, submitted without a history of RaI treatment, was diagnosed as suspicious for papillary carcinoma. The smears from patient 3 were signed out descriptively because the pertinent clinical history had not been provided. The FNAB specimens from the last three patients were correctly interpreted because of the history of RaI therapy provided. All six thyroid surgical specimens showed changes consistent with radiation injury, and none contained evidence of malignancy.

CONCLUSION

The study's findings demonstrate that the atypia produced by RaI may be severe, leading to an erroneous diagnosis of malignancy. Provision of the appropriate clinical history of Graves' disease treated with RaI may prevent this pitfall.