H3 G34-mutant high-grade glioma

H3F3A G34 (H3.3 G34)-mutant high-grade gliomas (HGG) are rare, and newly recognized infiltrating gliomas of the cerebral hemisphere. Here, we report the clinicopathological and molecular characteristics of four H3.3 G34-mutant gliomas in terms of its biological behavior compared to those of glioblastomas (GBMs) and H3 K27M-mutant diffuse midline gliomas (DMGs) of our hospital. The median age of the four patients with H3.3 G34 HGG was 44.5 years (14–66 years). Three patients had tumors in the cerebral hemisphere, whereas one patient had synchronous double tumors in the cerebral hemisphere and posterior fossa. All these tumors were high-grade glioma, but neither microvascular proliferation nor necrosis. They displayed uniform genetic and epigenetic signatures; ATRX-mutant, MGMT promoter-methylated, Olig2-negative, but IDH- and TERT promoter-wildtype. The median survival rate of H3.3 G34-mutant HGGs, IDH-was 23.5 months. In conclusion, H3.3 G34-mutant gliomas were unique HGGs with uniform genetic and epigenetic abnormalities, which suggested a single phylogenic origin. The median survival of H3.3 G34-mutant HGGs was better than those of IDH-wildtype GBMs and H3 K27M-mutant DMGs, but worse than that of IDH-mutant GBM. The tumor-infiltrating area and resectability may be the crucial parameters for the prognosis of the patients.