In 1956-7 the World Health Organization (CNS) resolved to develop a classification of tumors that would be used around the world. This was critical to be able to conduct clinical trials and to be able to compare results internationally. The first brain tumor WHO classification,published in 1979, was based on pathology. Changes were made in the subsequent three editions to reflect new knowledge from immunohistochemisty and genomics. The last WHO CNS classification in 2007 added eight "new" entities as well as some additional variants.
Diffuse intrinsic pontine gliomas have not be recognized as a class of tumors unto itself or a variant-- well, not yet by the World Health Organization. A review article points out that since 2007 there has been significant progress in understanding the molecular biology and genomics of GBMs. The article also suggests that there are several GBM variants including DIPG.
Perhaps the next WHO CNS classification revision will include diffuse intrinsic pontine glioma!
On the other hand, this would seem to be a significant deviation from the other classifications that have relied heavily on histopathology to define a tumor type. A WHO tumor classification based primarily on anatomic location would seem to be an uphill battle. However, clearly on clinical grounds DIPG is a fairly distinct entity primarily striking a particular age range (5-9) and failing therapies that have made some progress with adult GBMs. There have been recent advances showing these pediatric diffuse pontine gliomas are molecularly different from adult GBMs and even pediatric supratentorial GBMs.
Pediatric tumors known by location- this is not an isolated concept. Clinically tectal gliomas and optic gliomas are recognized by anatomical location. Recently, thalamic gliomas have been suggested as a distinct clinical group. We know brainstem gliomas are not all the same.
To make advances and aid in international communication, it would seem logical that DIPGs need to be recognized as an entity unto their own.
Reference:
WHO classification of the tumors of the central nervous system http://en.wikipedia.org/wiki/WHO_classification_of_the_tumors_of_the_central_nervous_system
The 2007 WHO Classification of Tumours of the Central Nervous System
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1929165/
Review Paper: Established and emerging variants of glioblastoma multiforme: a review of morphological and molecular features http://www.termedia.pl/Review-paper-Established-and-emerging-variants-of-glioblastoma-multiforme-review-of-morphological-and-molecular-features,20,19879,1,1.html
Thalamic high-grade gliomas in children: a distinct clinical subset?
http://neuro-oncology.oxfordjournals.org/content/13/6/680.long
