Comparison of core-needle biopsy and repeat fine-needle aspiration for thyroid nodules with inconclusive initial cytology

Purpose We aimed to compare the efficacy of ultrasound-guided core-needle biopsy (CNB) with repeat fine-needle aspiration (rFNA) cytology in thyroid nodules with inconclusive results in initial fine-needle aspiration cytology. Methods We studied 402 patients who required a repeat biopsy of thyroid nodules using ultrasound-guided CNB (n = 192) or rFNA (n = 210) because of inconclusive results in initial FNA, corresponding to categories I, III, and IV of the Bethesda System for Reporting Thyroid Cytopathology. If repeat biopsy results were benign (category II), suspicious malignancy (category V), or malignancy (category VI), they were defined as "diagnostic results". The diagnostic yield and performances of repeat biopsy were analyzed and compared between the rFNA and CNB groups. Results The diagnostic results were obtained significantly higher in the CNB group than in the rFNA group (72.4% vs. 52.4%; P < 0.001). In the subgroup analysis, the diagnostic results were significantly higher in the CNB group than in the rFNA group for patients of categories I and III (P < 0.001 in both) in initial FNA. However, in patients with category IV nodules, there were no significant differences in diagnostic results between the two groups (P = 0.46). Conclusion Compared to rFNA, ultrasound-guided CNB is useful and effective as a repeat biopsy option for thyroid nodules with non-diagnostic results (category I) and atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS) (category III) in initial FNA.