At the histo-molecular level, it was evidenced herein that adult diffuse hemispheric gliomas, H3 G34-mutant could present a PNET-like or a GBM-like morphology, lacked Olig2 expression, were most frequently immunonegative for ATRX, immunopositive for TP53, frequently demonstrated a methylated MGMT promoter, and lacked TERT promoter mutations. This evidence concerns the gene OLIG2 and glioblastoma.