Cellular Classification

Brain stem gliomas are classified according to their location, radiographic appearance, and histology (when obtained). Brain stem gliomas may occur in the pons, midbrain, tectum, dorsum of the medulla at the cervicomedullary junction, or in multiple regions of the brain stem. The tumor may contiguously involve the cerebellar peduncles, cerebellum, the cervical spinal cord, and/or thalamus. The majority of childhood brain stem gliomas are diffuse, fibrillary astrocytomas that involve the pons (diffuse intrinsic pontine gliomas [DIPG]), often with contiguous involvement of other brain stem sites.[1,2] The prognosis is extremely poor for these tumors. Focal pilocytic astrocytomas have a more favorable prognosis. These most frequently arise in the tectum of the midbrain, focally within the pons, or at the cervicomedullary junction where they are often exophytic, and they have a far better prognosis than diffuse intrinsic tumors.[3-5]

The genomic characteristics of DIPG appear to differ from those of most other pediatric high-grade gliomas and from those of adult high-grade gliomas. Approximately 80% of DIPG tumors have a mutation in a specific amino acid in one of two histone H3 genes (H3F3A or HIST1H3B).[6] These mutations are less common in non–brain stem pediatric high-grade gliomas and are uncommon in adult high-grade gliomas.[6,7] Other recurring DIPG genomic alterations include PDGFRA amplification in approximately 30% of cases, with lower rates of amplification observed for some other receptor tyrosine kinases (e.g., MET and IGF1R). DIPG tumors also commonly show deletion of the P53 gene on chromosome 17p.[8,9] The gene expression profile of DIPG similarly differs from that of non–brain stem pediatric high-grade gliomas, further supporting a distinctive biology for this subset of pediatric gliomas.[9]

Primary tumors of the brain stem are most often diagnosed based on clinical findings and on neuroimaging studies using magnetic resonance imaging.[10,11] Histologic confirmation of presumed DIPG is usually unnecessary. Biopsy or resection may be indicated for brain stem tumors that are not diffuse and intrinsic or when there is diagnostic uncertainty based on imaging findings. New approaches with stereotactic needle biopsy may make biopsy safer.[12]

1. Freeman CR, Farmer JP: Pediatric brain stem gliomas: a review. Int J Radiat Oncol Biol Phys 40 (2): 265-71, 1998.  [PUBMED Abstract]
   
   
2. Laigle-Donadey F, Doz F, Delattre JY: Brainstem gliomas in children and adults. Curr Opin Oncol 20 (6): 662-7, 2008.  [PUBMED Abstract]
   
   
3. Epstein F, McCleary EL: Intrinsic brain-stem tumors of childhood: surgical indications. J Neurosurg 64 (1): 11-5, 1986.  [PUBMED Abstract]
   
   
4. Edwards MS, Wara WM, Ciricillo SF, et al.: Focal brain-stem astrocytomas causing symptoms of involvement of the facial nerve nucleus: long-term survival in six pediatric cases. J Neurosurg 80 (1): 20-5, 1994.  [PUBMED Abstract]
   
   
5. Pollack IF, Pang D, Albright AL: The long-term outcome in children with late-onset aqueductal stenosis resulting from benign intrinsic tectal tumors. J Neurosurg 80 (4): 681-8, 1994.  [PUBMED Abstract]
   
   
6. Wu G, Broniscer A, McEachron TA, et al.: Somatic histone H3 alterations in pediatric diffuse intrinsic pontine gliomas and non-brainstem glioblastomas. Nat Genet 44 (3): 251-3, 2012.  [PUBMED Abstract]
   
   
7. Schwartzentruber J, Korshunov A, Liu XY, et al.: Driver mutations in histone H3.3 and chromatin remodelling genes in paediatric glioblastoma. Nature 482 (7384): 226-31, 2012.  [PUBMED Abstract]
   
   
8. Zarghooni M, Bartels U, Lee E, et al.: Whole-genome profiling of pediatric diffuse intrinsic pontine gliomas highlights platelet-derived growth factor receptor alpha and poly (ADP-ribose) polymerase as potential therapeutic targets. J Clin Oncol 28 (8): 1337-44, 2010.  [PUBMED Abstract]
   
   
9. Paugh BS, Broniscer A, Qu C, et al.: Genome-wide analyses identify recurrent amplifications of receptor tyrosine kinases and cell-cycle regulatory genes in diffuse intrinsic pontine glioma. J Clin Oncol 29 (30): 3999-4006, 2011.  [PUBMED Abstract]
   
   
10. Albright AL, Packer RJ, Zimmerman R, et al.: Magnetic resonance scans should replace biopsies for the diagnosis of diffuse brain stem gliomas: a report from the Children's Cancer Group. Neurosurgery 33 (6): 1026-9; discussion 1029-30, 1993.  [PUBMED Abstract]
    
    
11. Liu AK, Brandon J, Foreman NK, et al.: Conventional MRI at presentation does not predict clinical response to radiation therapy in children with diffuse pontine glioma. Pediatr Radiol 39 (12): 1317-20, 2009.  [PUBMED Abstract]
    
    
12. Cartmill M, Punt J: Diffuse brain stem glioma. A review of stereotactic biopsies. Childs Nerv Syst 15 (5): 235-7; discussion 238, 1999.  [PUBMED Abstract]