NTRK3 and fibrosarcoma: Genes encoding neurotrophin receptor kinases (TRK) have recently been implicated as oncogenic drivers in multiple tumour types including infantile fibrosarcoma, papillary thyroid cancer and, rarely, adult HGG.6,7 Three members of the TRK proto-oncogene family have been described: TRKA, TRKB and TRKC, coded by the NTRK1, NTRK2 and NTRK3 genes, respectively.8 TRK fusions have been identified at varying frequency in paediatric gliomas, including in 3 out of 7 cases of infant HGG in one study, and have a critical role in tumourigenesis in mouse models.9