Role of Core Needle Biopsy in the Management of Atypia/Follicular Lesion of Undetermined Significance Thyroid Nodules: Comparison with Repeat Fine-Needle Aspiration in Subcategory Nodules.

BACKGROUND The role of repeat fine-needle aspiration (RFNA) or core needle biopsy (CNB) has not been established in nodules categorized as atypia/follicular lesion of undetermined significance (AUS/FLUS). OBJECTIVE The purpose of this study was to retrospectively determine whether CNB is more useful for management decisions than RFNA at each subcategory of AUS/FLUS nodules. METHODS This study included 158 AUS/FLUS nodules (≥1 cm) from 153 consecutive patients who underwent both RFNA and CNB. The AUS/FLUS nodules were subcategorized into nuclear atypia (NA) and follicular lesions with other atypia (FOA). The diagnostic results and rate of determined management by RFNA and CNB were compared at each subcategory. The diagnostic values of RFNA and CNB for malignancy were evaluated in nodules with final diagnoses. RESULTS CNB showed a lower rate of AUS/FLUS diagnosis, higher rates of benign and follicular neoplasm or suspicious for a follicular neoplasm (FN/SFN) diagnoses (p ≤ 0.038), and marginally higher rates of malignant diagnosis than RFNA in the NA subcategory. CNB showed a higher rate of FN/SFN (p = 0.007) than RFNA in the FOA subcategory. CNB also demonstrated a higher rate of surgery decision than RFNA in both the NA subcategory (20.2 vs. 9.6%, p < 0.001) and FOA subcategory (20.8 vs. 5.6%, p = 0.007), and a higher rate of observation decision only in the NA subcategory (48.1 vs. 35.6%, p = 0.035). CNB demonstrated a higher diagnostic performance for malignancy overall in the nodules compared with RFNA. CONCLUSION CNB may be more useful for management decisions than RFNA in both the NA and FOA subcategories, and has the potential to be a first-line alternative diagnostic tool in initially diagnosed AUS/FLUS nodules.