Morphogenetic characteristics of glial tumors in adults per the WHO classifications of 2007, 2016, 2021. Changes in the classifications and their significance for clinical practice

The presented lecture is dedicated to analysis of morphogenetic characteristics of glial tumors in adults in the framework of the World Health Organization (WHO) classifications of 2007, 2016, 2021, changes in the classifications and their significance for clinical practice. This topic is important because the most difficult changes for neurosurgeons to understand in comparison of the WHO classifications of 2007, 2016 and 2021 involved sections on glial tumors and children’s tumors. The authors focus on increasing practical significance of genetic component in tumor characterization. The classification of 2007 was the last purely morphological classification of central nervous system tumors, it did not include genetic principles of tumor division in different groups. In the following years, knowledge on the significance of various mutations for prognosis of glial tumor progression and selection of optimal treatment based in genetic characteristics of the neoplasm has been actively accumulated. In the 2016 edition, morphological and genetic tumor characteristics were consolidated for the first time which was unquestionably a necessary step. Complex integrative analysis of glioma genomes has shown that genetic characteristics have higher prognostic value compared to the WHO Grade. In the classification of 2021, names of the tumors proposed in 2016 were changed, and practical significance of the genetic component in tumor characterization was increased. However, this can further complicate interpretation of histological diagnosis by practicing neurosurgeons. Implementation of the 2021 WHO classification in clinical practice assumes expansion of the spectrum of genetic diagnostic methods. The neurosurgical community should be ready to interpret morphogenetic results and select treatment tactics in tandem with oncologists based on genetic characteristics of the tumor.