Diffuse Hemispheric Glioma, H3 G34‐Mutant With Prominent Perivascular Invasion in a Middle‐Aged Man: A Case Report and Literature Review of Middle‐Aged and Elderly Cases

Diffuse hemispheric glioma, H3 G34‐mutant (DHG), is a newly defined pediatric‐type tumor in the 2021 WHO classification of central nervous system (CNS) tumors. DHGs harbor missense mutations at codon 35 of H3F3A (H3.3 G35R/V mutations) and exhibit diverse histopathological features, such as glioblastomas or CNS embryonal tumors. Regardless of histological variation, they demonstrate uniform immunohistochemical and molecular findings: Olig2 negative, ATRX loss, p53 positive, and MGMT promoter methylated. These tumors occur predominantly in the cerebral hemispheres of adolescents and young adults, while they are extremely rare in middle‐aged and elderly individuals. Here, we report a middle‐aged case of DHG with prominent perivascular invasion. The tumor initially demonstrated a focal glioblastoma‐like area, whereas the recurrent tumor predominantly showed perivascular spread of spindle cells. We reviewed previously reported DHG cases in middle‐aged and elderly patients and compared their clinicopathological features with those of adolescents and young adults.