Rare Embryonal Brain Tumors

Rare embryonal brain tumors (rEBTs) of the central nervous system (CNS) are a diverse category of extremely aggressive malignancies that primarily affect young children. Prior to 2016, these were collectively referred to as primitive neuroectodermal tumors (CNS-PNETs) or supratentorial primitive neuroectodermal tumors (sPNETs). Recent advances in molecular genomics have rendered better understanding into the biology and heterogeneity of these tumors, leading to the advent of a molecular categorization system making “sPNET” outdated and removed from the WHO 2016 classification of brain tumors. As newly described entities, the clinical features, biological heterogeneity, and treatment-related prognosticators for these rare tumors remain to be fully elucidated. This chapter aims to consolidate an overview of some of these rare entities including embryonal tumor with multilayered rosettes (ETMRs), pineoblastoma, CNS neuroblastoma FOXR2-activated, CNS tumor with BCOR internal tandem duplication, detailing the characteristic genetic profiles, and immunophenotypes, along with general treatment guidelines for these rare embryonal tumors of childhood. Atypical teratoid rhabdoid tumor (ATRT) is another such rare entity; however, it is described separately.