Diffuse midline glioma (DMG) is a rare type of cancerous brain tumor. It's most common in children between the ages of 5 and 10 years old, though it can also affect adults. The name means:

 - Diffuse: The cancer cells have spread beyond the tumor and into healthy brain tissue.
 - Midline: The tumor is found in the middle section of the central nervous system, usually the            thalamus, spinal cord, or brainstem, also called the pons.
 - Glioma: The tumor grew from glial cells, which are "helper" cells in the white matter of the                brain. This may also include certain categories of Diffuse Intrinsic Pontine Glioma (DIPG).
 - Source: MayoClinic.org

DIPG was reclassified as DMG when it was found that DIPG-like tumors, defined by similar histology and/or the H3 K27M mutation, could be found in other parts of the brain than the pons. For a long time, since 2016, there was only DIPG because prior classifications mostly relied on location in the pons, age of diagnosis, and findings under the microscope.

However, as molecular testing evolved and pathologists realized that many DIPGs had H3 K27M mutations, they started testing other tumors that looked similar under the microscope for the H3 K27M mutation. And in adults, the pontine location is not as common; more common in the thalamus, midbrain, and spinal cord.

This really illustrates the importance of genetic testing, because now adults who have this mutation, despite not being in the classic pons location, can qualify for FDA-approved targeted medications, such as Dordaviprone, and for clinical trials (some GMG trials have eligibility up to 60 years old).

EBCI Patient & Resource Navigators can help patients and caregivers better understand DPG results, explore testing resources, identify potential clinical trial opportunities, and prepare questions to discuss with their healthcare team.

Shreya Prakash
4235-444-2215
shreya@endbraincancer.org

This information is intended for educational purposes and is not a substitute for medical advice. Patients should discuss testing results and treatment decisions with their qualified healthcare provider.