Doctors and other medical scientists want learn about the biology of DIPG/DMG and to develop better ways to diagnose and treat patients with DIPG/DMG. To do this, they need more information about the characteristics of DIPG/DMG tumors. Therefore, they want to establish a central location for clinical information and tumor tissue collected from DIPG/DMG patients. The purposes of this study are: * To enroll patients diagnosed with DIPG/DMG in the International DIPG/DMG Registry and Repository. * To provide a central location for clinical information, scans, and tissue samples from patients with DIPG/DMG enrolled in the registry. * To collect tissue samples in order to study how DIPG/DMG works on the molecular level. Researchers may use the tissue samples to study molecules such as proteins and DNA. Proteins are needed for the body to function properly and DNA is the molecule that carries our genetic information. Other researchers will be able to use the stored samples in the future to learn more about DIPG/DMG. The information researchers get from the research studies will be kept in the registry along with the clinical information. * To help investigators around the world to work together to make more consistent diagnosis and better design of future research studies. We hope this will lead to better treatments for DIPG/DMG in the future.