When to repeat thyroid fine needle aspiration cytology?

The aim of of the study was to investigate the possible changes of primary fine needle aspiration (FNA) diagnoses after subsequent check ups. We investigated 948 thyroid nodules and the main indications for repeat FNAs were inadequate/indeterminate FNA findings and growing nodules at ultrasound check up. FNA findings were subdivided into inadequate, benign, low-risk lesion (includes cellular follicular lesion, suspicious of follicular/Hürthle cell neoplasm, atypical Hürthle cell hyperplasia), follicular/Hürthle cell neoplasm, high-risk lesion (includes lesions suspicious of malignancy), and malignant. Of the total of 948 nodules, repeat FNA diagnoses remained within the same category in 709 (75%) nodules. Out of 38 primary inadequate FNAs, 7 (18%) remained inadequate, 24 (63%) were benign, and 3 (8%) were categorized as high-risk/malignant. Out of 659 primary benign FNAs, 587 (89%) remained benign, and 11 (2%) were categorized as high-risk/malignant. Out of 169 primary low-risk lesion FNAs, 66 (39%) remained low-risk, 65 (38%) were benign, and 10 (6%) were categorized as high-risk/malignant. Out of 43 primary high-risk lesion FNAs, 20 (46%) remained high-risk, 2 (5%) were benign, 3 (7%) were categorized as a low-risk lesion, and 13 (30%) were categorized as malignant. Out of 35 FNAs that were primary follicular/Hürthle cell neoplasm, 27 (77%) remained follicular/Hürthle cell neoplasm, 1 (3%) was categorized as benign, 4 (11%) were categorized as a low-risk lesion, and 3 (8%) as high-risk/malignant. In conclusion, repeat thyroid FNA is useful in most cases of primary inadequate/indeterminate FNA findings, as well as in the evaluation of growing nodules.