What to Do for Atypia of Undetermined Significance in Pediatric Thyroid Nodules?

Objective: International guidelines recommend different approaches for the management of pediatric thyroid nodules with a finding of atypia of undetermined significance (AUS) on cytology. The American Thyroid Association (ATA) pediatric guidelines recommend surgery whereas the European Thyroid Association (ETA) guidelines recommend repeat fine-needle aspiration biopsy after six months. Our objective was to identify markers of malignancy in AUS cases and to discuss the management of pediatric AUS nodules. Methods: Specimens from pediatric patients who underwent surgery due to AUS cytology were re-evaluated and subcategorized according to the 2023 Bethesda classification. Results: Of the 20 cases included, 11 (55%) were histologically benign, while 9 (45%) were malignant. On the subcategorization of AUS, nuclear atypia was present in 14 patients (70%), and other atypia in 6 patients (30%). Of the cases with nuclear atypia, 64.3% were malignant (n=9), whereas no malignancy was detected in cases with other atypia (p=0.012). Among the cytopathological features, chromatin clearing, nuclear enlargement, and irregular margins were significantly associated with malignancy (p=0.035, p=0.003, and p=0.012, respectively). Adhering to ETA recommendations would delay diagnosis by at least 6 months in 45% of our malignant cases. Conversely, performing lobectomy according to ATA recommendations may lead to unnecessary surgery in 55% of our cases. Conclusion: Based on our findings, lobectomy appears to be a more appropriate approach in AUS cases but only when nuclear atypia is present, to avoid diagnostic delay and unnecessary surgery. Guidelines should be updated according to the latest Bethesda classification.