The role of thyroid FNA cytology in pediatric malignant lesions: An overview of the literature.

When one is dealing with pediatric thyroid lesions, fine-needle aspiration is the first diagnostic tool for the correct characterization of these nodules. Despite the apparent infrequency of thyroid cancers in children, recent data from the National Cancer Institute prove that the incidence has been increasing, especially in adolescents. With the same data, a higher prevalence of well-differentiated cancers can be estimated, with 90% diagnosed as papillary thyroid cancer. Nonetheless, some publications have demonstrated that some specific malignant variants are more frequent in children and have a more aggressive behavior that justifies the increased number of surgical procedures. For this reason, the American Thyroid Association recommends the performance of neck ultrasonography and fine-needle aspiration cytology (FNAC) for the evaluation of pediatric thyroid nodules. Accordingly, as reported in adult thyroid series, several authors have documented the high sensitivity and diagnostic accuracy of FNAC in pediatric series; they have also shared the same problematic issues encountered in adult populations, mostly in the diagnosis of indeterminate lesions. To provide precise clinical and/or surgical management, the correct cytological identification of specific malignant histotypes/entities should be mandatory because lymph nodes, distant metastases, and extrathyroidal infiltration are more frequent within specific histotypes. A perusal of the literature shows that their identification has not been extensively studied and investigated in cytological samples. This review focuses on the analysis of data from the literature on the evaluation of malignancies and specific morphological features in pediatric thyroid lesions. Cancer Cytopathol 2017;125:594-603. © 2017 American Cancer Society.