MGMT and glioma: Two additional molecular biomarkers essential to diagnosing and treating gliomas are represented by histone H3-K27M mutation and MGMT promoter methylation: assessment of H3-K27M is essential for the molecular diagnosis of diffuse midline gliomas, including most brainstem, thalamic, and spinal diffuse gliomas in children and adults; MGMT promoter methylation status guides treatment decisions about chemotherapy use.