Thyroid nodules occur in 1-2% of children, and identifying which nodules are malignant is often challenging. Cytologic evaluation facilitates the diagnosis of thyroid lesions (TLs), but in 10-40% of cases the interpretation is indeterminate. Patients with indeterminate diagnoses are often treated with hemithyroidectomy followed by completion thyroidectomy, if cancer is found in the initial specimen. Exposing patients to multiple surgeries increases costs and morbidity. The American Thyroid Association states that a combination of molecular markers is likely to optimize the management of patients with indeterminate cytology. However, few studies have addressed the molecular alterations present in pediatric TL. Twenty-seven thyroid carcinomas from patients 10 to 19 years of age were tested for alterations common in adult TL, including BRAF V600E mutation, RET fusions, and TERT promoter mutations. Mutation-negative cases were subsequently analyzed with a next-generation sequencing (NGS) mutation panel to search for additional targets. Histologic diagnoses included 12 classic papillary thyroid carcinomas (PTCs), 13 follicular variant PTCs, 1 medullary thyroid carcinoma, and 1 follicular carcinoma. Fourteen cases showed lymph node involvement, and 13 cases demonstrated lymphovascular invasion. The BRAF V600E mutation was detected in 10/27 cases, and RET fusions were detected in 6/27 cases. No TERT promoter mutations were identified in any of the cases. The NGS panel revealed additional RET and CTNNB1 pathogenic missense mutations. Our results demonstrate that molecular abnormalities are common in pediatric TLs and suggest that incorporation of molecular testing will be helpful in optimizing patient management.

This study confirms the high incidence of WWTR1-CAMTA1 and YAP1-TFE3 rearrangements in EHE and indicates that the staining pattern for TFE3 IHC is critical for specificity.

Low to intermediate histopathologic grade MECs are more common than high grade MEC in children. In contrast to adults, MECT1/MAML2 fusion transcripts occur with a frequency of 100% in our pediatric MEC series. Complete excision is the treatment of choice and is associated with excellent outcome. The role of radiotherapy is unclear, but may be indicated in patients with high grade tumors with positive surgical margins.

Key Points• Children with primary MDS should be tested for GATA2 mutations, regardless of karyotype, family history, or features of GATA2 deficiency.• Screening children with GATA2-MDS for somatic mutations may reveal mutations predictive of clinical outcomes.Approximately 10% of children with primary myelodysplastic syndrome (MDS) have germ line GATA2 mutations, leading to the proposal that all children with primary MDS and certain cytogenetic findings, including monosomy 7, be tested for germ line GATA2 mutations regardless of family history or other clinical features associated with GATA2 deficiency. In adults with familial GATA2-MDS, those with somatic mutations in ASXL1 experience rapid disease progression to acute myeloid leukemia (AML) and poor prognosis after stem cell transplantation; however, the prevalence of somatic mutations in primary pediatric GATA2-MDS is unclear. Here, we studied a cohort of 8 pediatric patients with MDS and lacking additional GATA2-associated clinical features or significant family history and identified heterozygous germ line GATA2 mutations in 5 patients, including 1 with a normal karyotype. For those with GATA2-MDS, we screened for somatic mutations in genes with prognostic relevance in AML/MDS, using a targeted next-generation sequencing panel.Although no somatic mutations in ASXL1 were observed, somatic mutations were found in RUNX1, SETBP1, IKZF1, and CRLF2. One subject with deleterious mutations in RUNX1, SETBP1, and IKZF1 rapidly progressed to AML with disease that was refractory to treatment.Our findings confirm the importance of GATA2 testing in primary pediatric MDS, even in the absence of other clinical features of GATA2 deficiency. Further, similar to what has been observed in adults with GATA2-MDS, somatic mutations with potential prognostic effect occur in children with MDS associated with mutations in GATA2.