ASPIRATION CYTOLOGY OF I-131 INDUCED THYROIDITIS - A CASE-REPORT

BACKGROUND: Fine needle aspiration (FNA) has become nit indispensable diagnostic tool for the investigation Of thyroid nodules. Although I-1 31 may induce morphologic changes similar to those associated with ext ernal radiation, it known diagnostic pitfall, the cytology literature an the subject is very sparse. This case exemplifies the thyroid cytol ogic changes associated with I-131 exposure. CASE: A 50-year-old male with a remote history of I-131 exposure had an indurated thyroid on ro utine physical examination. FNA was interpreted as positive for malign ant cells, and subsequently a total thyroidectomy was performed. Revie w of the cytologic sample revealedfollicular cells with focal, marked cytologic atypia, abundant colloid, stromal fragments, and lymphocytes . The thyroidectomy specimen consisted of an indurated and nodular gla nd showing architecture distortion by micronodule formation, lymphocyt ic infiltrates, interstitial fibrosis and follicular atrophy. Marked n uclear atypia was seen in the follicular cells. CONCLUSION: FNA of thy roid glands exposed to I-131 may show significantly large, atypical fo llicular cells in addition to classical changes of nodular goiter and/ or chronic lymphocytic thyroiditis. Although the clinical history and the diffuse nature of the process may favor a benign process in most c ases, the presence of marked atypia could lead to a malignant diagnosi s. Pathologists, therefore, should exercise extreme caution in interpr eting cases with I-131 exposure.