Age-related aspects of glioma: current understanding. Literature review

The updated 2021 WHO Classification of Central Nervous System (CNS) Tumors introduces, for the first time, an age-based approach to glioma classification, leveraging advances in molecular biology and epigenetics of CNS tumors. This classification groups gliomas within the category "Gliomas, glioneuronal tumors, and neuronal tumors," distinguishing between adult-type and pediatric-type diffuse gliomas, corresponding to low-grade and high-grade malignancies (LGG and HGG), highlighting the fundamental role of age in gliomagenesis. A review of current literature deepens the understanding of age-related characteristics, differences, and patterns in gliomagenesis across age groups, which is essential for effective diagnosis and treatment. Pediatric-type and adult-type low-grade gliomas (pLGG and aLGG) differ in location, biological behavior, and molecular-genetic profiles. Inherited syndromes (e.g., NF-1, TSC) associated with glioma development are linked to specific LGG subtypes occurring in childhood, adolescence, and adulthood. Moreover, pLGG differs from aLGG in its potential for malignant transformation and spontaneous regression, as well as in mutations affecting the MAPK (mitogen-activated protein kinase) pathway. While pediatric-type and adult-type high-grade gliomas (pHGG and aHGG) share histological features, they differ in location, biological behavior, molecular-genetic profiles, and prognosis. A major distinction between aHGG and pHGG lies in mutations such as IDH 1/2, EGFR gene expression, TERT mutations, chromosome alterations (+7/-10), and TP53 mutations, all contributing to a poorer prognosis in HGG gliomas. Additionally, changes in histone proteins H3.3 or 3.1 (H3.3 K27 and H3 G34) in pHGG, as opposed to aHGG, carry diagnostic and prognostic significance. An analysis of data on glioma epidemiology, risk factors, and characteristic molecular-genetic features considering age is provided. The next publication will cover certain clinical aspects of this issue.