[Thyroid nodules in children: risk of malignancy for each Bethesda category]

Thyroid nodules are unusual findings in children. Some authors highlight the higher rate of malignancy in this group. The Bethesda system, created in adults to stratify thyroid nodules according to the risk of malignancy, constitutes a reference system for the management of this pathology. The American Thyroid Association promotes its use in the pediatric population, although there is no available data showing an equivalent risk. The aim of this study was to assess the risk of malignancy represented by each Bethesda stage in a pediatric study population.

A retrospective cohort study was performed in pediatric patients with thyroid nodules biopsied by fine needle aspiration, during the period 2005-2017. During the follow-up, the outcome was assessed by comparing the Bethesda stage (cytology) with the surgical specimen histology. For patients not surgically treated, Bethesda Class was compared with the clinical and imaging follow up.

105 patients with fine needle aspiration of a thyroid nodule were analyzed and classified by the Bethesda system. 47 patients were excluded for incomplete follow-up. All Bethesda I nodules were benign, 6.6% of Bethesda II were malignant and all Bethesda IV, V and VI nodules were histologically malignant.

The rate of malignancy among patients with Bethesda II, IV, V and VI was higher than published in Bethesda classification for adults. The risk of malignancy in pediatric patients might be greater than expected. These results may have a significant impact on follow-up strategies and also in therapeutic algorithms.