Overview
Diffuse midline glioma (DMG) is a poorly-confined and invasive tumor most commonly found in children, although with more biomarker testing being performed, it is increasingly being diagnosed in young adults. It originates from glial cells which surround and support nerve cells. Diffuse midline glioma occurs at the midline of the brain, which is the central area between the right and left sides. Pediatric diffuse midline glioma primarily occurs in the brainstem or pons – those located in the pons are also called diffuse intrinsic pontine gliomas (DIPG) – or they occur in the thalamus. Diffuse midline gliomas in adolescents and adults are primarily located in the thalamus or in the spinal cord. Importantly, true midline glioma has an alteration in H3K27 which is required for the diagnosis. DMG often presents with a triad of signs and symptoms that include paralysis of the cranial nerves, impact to muscle movement like spasticity or weakness, and lack of muscle coordination which can lead to clumsy movement and difficulty with balance and walking.
Biomarker testing, also called molecular testing, plays an important role in the diagnosis and subtyping of ependymomas. The 2021 WHO Classifications note the presence of four subtypes of DMGs based on their biomarkers:
- H3.3 p.K28M (K27M)-mutant
- H3.1 or 3.2 p.K28M (K27M)-mutant
- H3-wildtype with EZHIP overexpression
- EGFR-mutant
2021 WHO CNS Grade
A tumor grade describes how normal or abnormal tumor cells appear under a microscope. In lower grade tumors like grade 1, the cells look close to normal. In higher grade tumors like grade 4, the cells look more abnormal. Diffuse midline glioma is considered grade 4.
Statistics
- Average Annual Age-Adjusted Incidence Rate: 0.06 per 100,000
- Median Age at Diagnosis: 16 years
Survival
Survival rates compare the percentage of people living with a particular diagnosis at a particular point in time compared to the general population.
- Five-Year Relative Survival Rate: 42.2%
Treatment Options
Every person living with a brain or CNS tumor is unique. If you have been diagnosed with a brain or CNS tumor and would like to better understand your treatment options, it is important to work with your health care team to decide the best course of treatment for you. You may also consider getting a second opinion or reaching out to our Personalized Support and Navigation team to learn more.
References
The above information is from the World Health Organization (WHO) Central Nervous System (CNS) Tumors Classification of Tumours and the Central Brain Tumor Registry of the United States (CBTRUS) unless otherwise noted. It was written by NBTS staff and medically reviewed by members of the NBTS Scientific and Medical Advisory Council.
Last updated April 22, 2025
Please speak with your health care provider for more information about your tumor type, biomarkers, and treatment options, including clinical trials.
