Superior Diagnostic Yield of Core Needle Biopsy Over Fine Needle Aspiration in Diagnosing Follicular-Patterned Neoplasms: A Multicenter Study Focusing on Bethesda IV Results.

Objective: To compare the diagnostic outcomes of core needle biopsy (CNB) and fine-needle aspiration (FNA) using Bethesda IV as a test-positive criterion for diagnosing follicular-patterned neoplasms in a large multicenter cohort.

Materials and methods: This retrospective study included 5463 thyroid nodules ≥1 cm from 4883 patients (4019 females, 864 males; mean age 53.8 years) that underwent FNA or CNB across 26 hospitals in Korea between June and September 2015. The final diagnosis in cases diagnosed as Bethesda IV (follicular neoplasm) in biopsies were confirmed by surgical pathology. The primary study outcome was the diagnostic yield, defined as the proportion of nodules with follicular-patterned neoplasms confirmed at surgery after receiving Bethesda IV results on biopsy (FNA or CNB), among all that underwent biopsy. Secondary outcomes included false referral rate (FRR) and positive predictive value (PPV). All nodules were analyzed before matching (823 and 4640 nodules for CNB and FNA, respectively) and after nodule matching in a 1:2 ratio (799 and 1571 nodules, respectively) according to age, sex, nodule size, and Korean Thyroid Imaging Reporting and Data System (K-TIRADS) category. Additionally, the diagnostic yields of various histological subtypes of follicular-patterned neoplasms and nodule subgroups were analyzed.

Results: CNB demonstrated a significantly higher diagnostic yield than FNA both before (9.0% vs. 0.5%; P < 0.001) and after matching (9.0% vs. 0.6%; P < 0.001). CNB consistently had higher diagnostic yields than FNA for most histological subtypes and all subgroups. FRR was not significantly different between the CNB and FNA groups after matching (0.4% vs. 0.1%; P = 0.337). The PPV was consistently greater than 90% for both methods, with no significant difference.

Conclusion: CNB had a higher diagnostic yield than FNA for follicular-patterned neoplasms, with no significant difference in FRR using Bethesda IV as the test-positive criterion.