ABSTRACT
PURPOSE: To determine the diagnostic benefit of repeated fine-needle aspiration (RFNA), according to the US patterns in thyroid nodules initially diagnosed as atypia/follicular lesion of undetermined significance (AUS/FLUS).
MATERIALS AND METHODS: This study included 273 consecutive nodules in which follow-up RFNA was performed among 502 thyroid nodules (≥1 cm) initially diagnosed as AUS/FLUS from January 2010 to December 2014. The diagnostic benefit of obviating unnecessary diagnostic surgery was determined when the RFNA cytology result was benign. We assessed the rate of diagnostic benefit, surgery decision (RFNA result of category 4, 5, 6), and conclusive diagnostic result (RFNA result of category 2,4,5,6) on RFNA according to US patterns of nodules defined by Korean Thyroid Imaging Reporting and Data System (K-TIRADS).
RESULT: The diagnostic benefit of benign RFNA result was found in 49% in K-TIRADS 3, 37.8% in K-TIRADS 4, and 28% in K-TIRADS 5 nodules, and there was a decreasing trend of the diagnostic benefit rate on RFNA with increasing K-TIRADS score (P=0.034). The surgery decision was made in 3.4% in K-TIRADS 3, 11.2% in K-TIRADS 4, and 28% in K-TIRADS 5 nodules (P<0.001). There was no difference of conclusive RFNA results among K-TIRADS scores (p=0.773). The AUS/FLUS subcategory and nodule size was not significantly associated with the diagnostic benefit of RFNA. The false negative rate of benign cytology result of the first RFNA was 1.7%~2.3% according to the criteria of final benign diagnosis.
CONCLUSION: The diagnostic benefit of RFNA to obviate unnecessary surgery was found at least 28% in initially diagnosed AUS/FLUS nodules. Therefore, repeated biopsy may be helpful to reduce the unnecessary diagnostic surgery even in AUS/FLUS nodules with high suspicion (K-TIRADDS 5) US pattern.