Paediatric type diffuse high grade gliomas in the WHO CNS5 classification: What the pathologist needs to know?

Pediatric-type of diffuse high-grade gliomas (HGG) are classified as a distinct group in the current fifth edition of WHO classification. This group of high-grade tumors is no more called as glioblastoma (GBM), which has been reserved for adult isocitrate dehydrogenase (IDH)-wild type HGG. These tumors are uncommon as compared to embryonal tumors and low-grade gliomas (LGG). Pediatric-type of diffuse HGG biologically differs from their adult counterparts in that they are therapeutically less sensitive to alkylating chemotherapies. They comprise a heterogeneous group of molecularly defined tumors - predominantly histone gene altered, less common receptor tyrosine kinase (RTK)-mediated, and syndrome-associated. This review provides an overview of these uncommon tumors and discusses the diagnostic approach of this heterogeneous group of tumors.