Background: Thyroid nodules with fine-needle aspiration (FNA) readings of nondiagnostic or atypia of undetermined significance (AUS), also referred to as follicular lesion of undetermined significance (FLUS) are problematic for their optimal management. The usefulness of performing a core-needle biopsy (CNB) to clarify whether these nodules are benign or malignant has not been established. The purpose of the present study was to determine whether CNB provides better diagnostic information than repeat FNA (rFNA) in thyroid nodules having nondiagnostic or AUS/FLUS readings.
Materials and methods: The Bethesda System for Reporting Thyroid Cytopathology was used for FNA readings and for CNB readings. The study included 225 thyroid nodules from 220 consecutive patients who previously had nondiagnostic (Group N-DIAG, n=64) or AUS/FLUS (Group AF, n=161) FNA readings. All patients simultaneously underwent rFNA and CNB of each nodule. The nondiagnostic and AUS/FLUS readings by rFNA and by CNB were compared. The diagnostic sensitivities of rFNA and CNB for malignancy in thyroid nodules were also assessed. Statistical analysis was performed using a McNemar's test.
Results: In N-DIAG Group, the nondiagnostic readings for the CNBs were lower than that those for rFNAs (1.6% vs. 28.1%, p<0.001). In the AF Group, the AUS/FLUS readings for the CNBs were lower than those for the rFNAs (23.6% vs. 39.8%, p<0.001). The inconclusive diagnoses (nondiagnostic or AUS/FLUS) for the CNBs were lower than those for the rFNAs in Group N-DIAG (12.5% vs. 45.3%, p<0.001) and Group AF (26.7% vs. 49.1%, p<0.001). The sensitivity of CNB for thyroid malignancy was higher than that of rFNA in Group N-DIAG (100% vs. 71.4%, p=0.125) and Group AF (78.5% vs. 55.4%, p<0.001).
Conclusion: After patients have had one FNA of a thyroid nodule yielding inconclusive diagnostic results (nondiagnostic or AUS/FLUS), CNB is more useful than rFNA for reducing the frequency of inconclusive diagnostic results. CNB will improve the diagnostic performance for malignancy more than rFNA in thyroid nodules that on the first FNA had nondiagnostic or AUS/FLUS readings.