Pediatric diffuse intrinsic pontine gliomas (DIPGs) are brain tumors that are diagnosed in children (peak incidence 5-9 years old). They make up around 10% of all pediatric brain tumors.
They are found in the pons (the middle portion of the brainstem), and, grow throughout (“infiltrate”) the pons, taking up at least half of this important structure. They can grow into other area of the brainstem, and grow into the CSF-filled fourth ventricle next to the pons.
DIPGs are tumors that arise from precursors of astrocytes – supportive cells of the brain named for their star-like shape. DIPGs are glial tumors (can be grade I through IV) that arise in the pons of the brainstem. They are fast growing tumors and tend to behave aggressively.
Recent research has shown that 80% of pediatric DIPGs are driven by mutations in histone genes H3F3A (H3.3) and HIST1H3B (H3.1), which are proteins scaffolds for DNA. As these mutations have important implications for tumor behavior, treatment, and prognosis, DIPGs with a histone mutation are pathologically diagnosed as "H3 K27M-mutated diffuse midline glioma."
Other important genes that are mutated in DIPG include the ACVR1 gene, which is involved in developmental regulation, the tumor suppressor gene TP53 (p53), and other genes that result in growth and proliferation of DIPG cells, including MYC, PDGFRA and PI3KCA . The molecular features of a DIPG may impact tumor prognosis and treatment response. Current investigational therapies are adapted to these molecular features.