[Neuropathology of medulloblastomas and other CNS embryonal tumors : Precision diagnostics through the integration of genetic markers].

The revised WHO classification of tumors of the central nervous system (CNS) in 2016 introduced the concept of the "integrated diagnosis." The definition of medulloblastoma entities now requires a combination of traditional histological information with additional molecular/genetic features. To define the histopathological component of the medulloblastoma diagnosis, tumors have to be assigned to one of the four histological entities: classic, desmoplastic/nodular (DNMB), extensive nodular (MBEN), or large cell/anaplastic (LC/A) medulloblastoma. The genetically defined component is one of the four entities: "WNT activated", "SHH activated and TP53 wildtype", "SHH activated and TP53 mutant", or "non-WNT/non-SHH medulloblastoma." Robust and validated methods are available that allow a precise diagnosis of these medulloblastoma entities according to the updated WHO classification and for differential diagnostic purposes. An immunohistochemical analysis of protein markers including ß‑Catenin, Yap1, p75-NGFR, Otx2 and p53, in combination with targeted sequencing and chromosomal copy number assessment (such as FISH analysis for MYC genes), allows a precise stratification of patients for risk-adapted treatment. The group of other embryonic tumors of the central nervous system includes embryonic tumors with multilayered rosettes (ETMR), which frequently carry an amplification of the micro-RNA cluster C19MC and the (ganglio-)neuroblastomas of the CNS. These rare tumors can also be identified by characteristic genetic and immunophenotypic features.