Repeat Fine Needle Aspiration Cytology (FNAC) in Thyroid Does Not Help in Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/FLUS)

Although the current recommendation in the category of “Atypia of undetermined significance/follicular lesion of undetermined significance” (AUS/FLUS) is a repetition of fine needle aspiration cytology (FNAC), it does not solve the problems. Our aim is to analyze the effectiveness of FNAC repeat in AUS/FLUS cases by comparing it with clinical and ultrasonographic criteria and to contribute to patient management. In our institution, 138 patients’ results, of those who were operated with AUS/FLUS FNAC between 2014 and 2019 and who had definite pathological diagnoses with clinical-pathological-radiological data, were examined. We divided the AUS/FLUS cases in our center into those with and without repeat FNAC (rFNAC), and we evaluated those with definite pathological results of these nodules with all clinical radiological data. We found that the incidence of malignancy increased significantly as the nodule size increased (2.6 cm) and in the presence of microcalcification in all nodules whose initial biopsy result was AUS/FLUS ( p = 0.047, p = 0.019, respectively). The malignancy rate was 19.8% (18/91 cases) in cases without rFNAC and 23.4% (11/47 cases) in nodules with rFNAC. The incidence of malignancy was found to be higher in patients with nodules of 2 cm and larger in rFNAC cases ( p = 0.043), and in patients with solid and microcalcified nodules in cases without rFNAC, and the results were significant ( p values 0.037 and 0.046, p < 0.05, respectively). It was remarkable that the incidence of malignancy increased with advanced age (57.5 ± 14.2 years, p = 0.017) in rFNAC cases. No relationship was found between nodule size and advanced age in cases after rFNAC, and other clinical and radiological features other than the relationship between solid and microcalcified nodule and malignancy in cases without rFNAC. We found a significant correlation between a microcalcific and solid nodule larger than 2 cm and malignancy in elderly patients diagnosed with AUS/FLUS after the first biopsy. We recommend direct surgery without repeat FNAC in the management of cases with all of these criteria.