The diagnosis of DIPG  is mainly based on MRI images. If the symptoms and MRI studies are not typical, a stereotactic biopsy may be required to make a diagnosis. In this case, a small hole is drilled in the skull. A needle will then be inserted through this hole to take a small piece of tissue for testing. A pathologist will examine the sample and make a diagnosis, gaining information about the tumor’s molecular profile. This procedure is safe and routinely done.