Molecular genetics of ependymomas and pediatric diffuse gliomas: a short review

Here, we review the recent literature on molecular discoveries in ependymomas and pediatric diffuse gliomas. Ependymomas can now be categorized into three location-related subgroups according to their biological profile: posterior fossa ependymomas, group A (PFA) and B (PFB), and supratentorial ependymomas. Although no recurrently mutated genes were found throughout these groups of ependymomas, PFA exhibited a CpG island methylator phenotype, PFB was associated with extensive chromosomal aberrations, and the C11orf95-RELA fusion gene was frequently observed in supratentorial ependymomas. Meanwhile, it has now become apparent that pediatric diffuse gliomas have a distinct genetic status from their adult counterparts, even though they share an indistinguishable histology. In pediatric low-grade diffuse gliomas, an intragenic duplication of the portion of FGFR1 encoding the tyrosine kinase domain (TKD) and rearrangements of MYB/MYBL1 were found recurrently and mutually exclusively. As for non-brainstem high-grade tumors, in addition to H3F3A, TP53, and ATRX mutations, which were frequently observed in older children, recurrent fusions involving NTRK1, NTRK2, and NTRK3 were reported in infants younger than 3 years of age. Moreover, in diffuse intrinsic pontine gliomas (DIPG), recurrent somatic mutations of ACVR1 were found in association with HIST1H3B mutations.