ESPE Abstracts

Introduction: Data on atypia of undetermined significance (AUS) in thyroid fine needle aspiration biopsy in children is limited. The American Thyroid Association (ATA) pediatric guideline recommends surgery, while the European Thyroid Association (ETA) recommends fine-needle aspiration biopsy (FNAB) repetition after 6 months. The aimof this study is to determine the markers of malignancy in AUS in children and to discuss the approach to AUS.

Materials and Methods: The specimens of the 20 patients who underwent surgery between 2009 and 2023 due to thyroid nodules with AUS cytology on FNAB were re-evaluated by the same pathologist. FNAB samples were subcategorized according to the Bethesda System for Reporting Thyroid Cytopathology 2023.

Results: On the histological follow-up of the cases, 11 (55%) were benign [follicular adenoma=1 (9.1%), nodular hyperplasia=8 (72.7%), chronic lymphocytic thyroiditis=2 (18.2%)], while 9 were malignant (45%), [Papillary thyroid carcinoma (PTC)=4 (44.4%), Follicular Variant-PTC=2 (22.2%), papillary microcarcinoma =3 (33.3%)]. Ultrasonographic features were not associated with malignancy. In the subcategorization of AUS, nuclear atypia was present in 14 patients (70%), other atypia in 6 patients (30%). Of the cases with nuclear atypia, 64.3% were malignant (n = 9), while of the cases while no malignancy was detected in other atypia (P = 0.008). Cytological features such as chromatin clearing, nuclear enlargement, and irregular margins were associated with malignancy (P = 0.025, P = 0.002, P = 0.02, respectively).

Conclusion: There is a conflict in the recommendations of the ATA and ETA regarding the management of AUS. Following ETA recommendations with repeat FNAB in 6 months reduces the risk of unnecessary surgery, but may delay diagnosis in malignant cases. Our data suggests that adhering to ETA recommendations would delay diagnosis by at least 6 months in 45% of malignancies, a considerable risk. When we perform lobectomy according to the ATA recommendation for our cases, 55% of cases undergo unnecessary surgery. In our study, due to the fact that 64.3% of AUS cases with nuclear atypia were malignant and none of the AUS cases with other atypia were malignant, performing lobectomy only for nuclear atypia would increase the malignancy rate to 64.3% among those operated on, while reducing the rate of unnecessary surgery to 35.7%. In conclusion, the association between nuclear atypia and malignancy has been clearly demonstrated, and lobectomy appears to be a more appropriate approach in AUS cases with nuclear atypia to avoid diagnostic delay and unnecessary surgery. Guidelines should be updated according to the latest Bethesda classification.