Molecular pathology of paediatric central nervous system tumours

Advances in our understanding of the biology of paediatric central nervous system (CNS) tumours have encouraged pathologists to use molecular markers alongside histopathological analysis for disease classification or prognostication and treatment stratification. In this article, we review molecular genetic alterations in paediatric CNS tumours, including those in low-grade and high-grade gliomas, ependymomas, and embryonal tumours. Some of these molecular changes with clinicopathological utility have been used for the first time in the most recent edition of the World Health Organization (WHO) classification of CNS tumours to define entities like ependymoma, RELA fusion-positive or diffuse midline glioma, H3 K27M-mutant. The classification of paediatric CNS tumours is entering a new era when histopathologists must work with molecular genetic data and their molecular pathology colleagues to provide an optimal diagnostic evaluation for their patients and clinical colleagues.