Gliomas are the common primary central nervous system CNS (brain tumor) and require proper classification and grading.
CNS tumor classification has in the past been based on histopathology and ancillary tests. The paradigm shift due to quantum increase in molecular knowledge of these tumors has lead to inclusion of newer entities, nomenclature, treatment options and prognosis. The latest WHO edition and recent updated literature including cIMPACT highlights various molecular changes important for accurate classification of CNS tumors .
The CNS tumor grading being entity specific and clinically driven is different from Non CNS tumors. The CNS tumor grading in current scenario of modern therapies is still debatable as stated below for instance.
A WNT- acitvated medulloblastoma, an embryonal tumor, is responsive to therapeutic regime with long term survival. Assigning grade 4 to it could given an incorrect impression of the prognosis.
At the other end a midline, morphological grade 2 tumor but H3K27M positive may behave like Grade 4 tumor and may falsely implicate a good biological behaviour. These examples reiterate the importance of theranostic and molecular testing for classification, grading and prognosis of all CNS tumors.
The recent literature and WHO encourages the use of molecular parameters for impactful prognostic information.
Tying to keep abreast with all the knowledge RGCIRC has included in their IHC armamentarium CNS specific Immuno markers.
The Glioma panel includes GFAP, S100, P53, EMA, IDH1 (R132H), ATRx, H3K27M, H3K27Me3, H3.3G34R, H3.3G34V to name the crucial ones. The ependymoma which have been reclassified genetically require YAP1 by IHC or FISH.
Classification of Medulloblastoma group- B-Catenin, YAP1, GAB1 IHC are in use.
The Department CNS panel includes reflex code for molecular testing, whenever required. The Molecular Deptt. of RGCI has MGMT promotor methylation by RTPCR, 1p19q codeletion by FISH. And can boast of a CNS specific NGS panel (Oncomine V3) which includes IDH1, ATRx, CDKN2A, CDKN2B, RELA, FGFR to name a few.
The above said markers cover only the initial panel of the non ending list and represent our understanding in the field at a particular stage of evolution of the CNS tumors.
IDH MUTATIONAL TESTING BY IHC IDH1 ...