Sporadic pediatric papillary thyroid carcinoma harboring the ETV6/NTRK3 fusion oncogene in a 7-year-old Japanese girl: a case report and review of literature

Background: There have been great concerns about pediatric thyroid cancers after the accident at the Fukushima Daiichi Nuclear Power Plant in 2011. Case presentation: We report a case of a 7-year-old Japanese girl with sporadic papillary thyroid carcinoma (PTC) harboring an ETV6/NTRK3 rearrangement. The patient presented with tumors in both lobes and underwent thyroidectomy followed by radioactive iodine (RAI) ablation. Histopathology showed a classic type of PTC with cervical lymph node metastasis. Conclusions: Genetic evaluation showed ETV6/NTRK3 fusion but no BRAF mutations or RET/PTC rearrangements. RET/PTC rearrangement and BRAF mutations often contribute to the pathogenesis of PTC; however, rearrangements of NTRK genes are relatively rare in pediatric PTC. Although NTRK rearrangement has been shown to often present unique pathological types and infiltrative architectures in the western population, such findings were not observed in this patient. Thus, the present case of classic PTC with ETV6/NTRK3 rearrangement highlights the disparate collection of clinic-pathological features compared to the trend in the western population. We therefore emphasize the need to further accumulate clinical as well as genetic data in pediatric PTCs.