Diffuse midline gliomas are rare and aggressive brain tumors that occur in midline structures like the brainstem, thalamus, or spinal cord. They mainly affect children and have a very poor prognosis, with median survival of 9-20 months. A defining characteristic is a mutation in the H3K27 gene. Treatment involves biopsy for diagnosis, followed by radiation and chemotherapy, but there is no standard chemotherapy regimen. Even with treatment, less than 10% of patients survive more than 2 years.