NASBS

North American Skull Base Society

2025 Poster Presentations

2025 Poster Presentations

 

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P175: MOLECULAR MARKERS IN GLIOMAS: A PRACTICAL REVIEW AND ALGORITHM PROPOSAL
Maria I Ocampo-Navia, MD; Felipe Marín Navas, MD; Mariana Agudelo-Arrieta, MD; Alex Taub-Krivoy, MD; Oscar H Feo Lee; Pontificia Universidad Javeriana

Gliomas, heterogeneous glial cell malignancies, constitute 26.3% of all CNS tumors and are known for extensive infiltration of the brain parenchyma. Glioblastoma, the most common primary malignant brain tumor, accounts for 14.2% of all CNS tumors, 50.9% of all CNS malignant tumors, and 60.2% of gliomas. In the pediatric population, gliomas account for 51.1% of all brain and other CNS tumors in children and adolescents. Most cases are sporadic; however, certain familial tumor syndromes have been associated with gliomagenesis, including Turcot syndrome, Li Fraumeni syndrome, neurofibromatosis type 1 and 2, tuberous sclerosis, and Lynch syndrome. The classification of CNS tumors has evolved from the groundbreaking work of Bailey and Cushing in 1926 to the 1979 WHO classification and the recent WHO CNS5 edition, which utilizes advanced histological and molecular techniques for precise diagnosis and grading. This approach integrates molecular profiling and genomic analysis, surpassing traditional methods and providing comprehensive insights into tumor biology. By enhancing diagnostic accuracy and understanding tumor behavior, this classification enables tailored therapeutic strategies, representing a significant advancement in neuro-oncology. Currently, gliomas are categorized into the group gliomas, glioneuronal tumors, and neuronal tumors, further divided into adult-type diffuse gliomas, pediatric high-grade diffuse gliomas, pediatric low-grade diffuse gliomas, and circumscribed astrocytic gliomas. This study aims to provide an updated practical review of the WHO CNS5 updates, focusing on the most important molecular biomarkers in the diagnosis of gliomas in both adult and pediatric populations, and to present a molecular diagnostic algorithm for gliomas.

Figure 1. Diagnostic algorithm for the integrated classification of adult-type diffuse gliomas. The presence and absence of diagnostically most relevant mutations are presented in green (non-altered) and red (altered) boxes. In patients aged > 55 years with a histologically typical glioblastoma, without a pre-existing lower grade glioma, with a non-midline tumor location and with retained nuclear ATRX expression, immunohistochemical negativity for IDH canonical mutation (IDH1 p.R132H) suffices for the classification as IDH-wildtype glioblastoma. In all other instances of adult diffuse gliomas, a lack of IDH canonical mutation (IDH1 p.R132H) should be followed by IDH1 and IDH2 DNA sequencing to detect or exclude non-canonical mutations. IDH-wildtype diffuse astrocytic gliomas without necrosis or microvascular proliferation should be tested for EGFR amplification, TERT promoter mutation and a +7/-10 cytogenic signature. TERT promoter mutation and MGMT promoter methylation are prognostic markers in oligodendrogliomas and Glioblastoma, respectively. EGFR: Epidermal growth factor receptor, H3: Histone-3, IDH: isocitrate dehydrogenase, TERT: Telomerase reverse transcriptase

Figure 2. Diagnostic algorithm for the integrated classification of pediatric low-grade diffuse gliomas and circumscribed astrocytic gliomas Pediatric type low-grade diffuse gliomas are showed in the orange boxes and circumscribed astrocytic gliomas are depicted in the green boxes. Some of the gliomas with MAPK-pathway alterations present more than one characteristic mutation, the color of the arrows indicates the most frequent mutations presented in each glioma type. H3: Histone-3, IDH: isocitrate dehydrogenase, MAPK: ras-mitogen activated protein kinase, FGRF: Fibroblast growth factor receptor, * These types of tumors do not have an established CNS WHO grade yet.

Figure 3. Frequent locations of pediatric low-grade diffuse gliomas and circumscribed astrocytic gliomas. PLNTY and PXA commonly present in the temporal lobe, PXA is usually a superficially located cortical mass. On the other hand, SEGA usually presents near the foramen of Monro and chordoid glioma in the third ventricle. HGAP and PA show frequent cerebellar locations. The location of the angiocentric glioma; diffuse low-grade glioma, MAPK pathway-altered,; astroblastoma and diffuse astrocytoma, MYB/MYBL1-altered is usually hemispheric. HGAP: high-grade astrocytoma with piloid features, PA: pilocytic astrocytoma, PLNTY: Polymorphous low-grade neuroepithelial tumor of the young, PXA: pleomorphic xanthoastrocytoma, SEGA: subependymal giant cell astrocytoma.

Figure 4. Diagnostic algorithm for the integrated classification of pediatric high-grade diffuse gliomas Age and location should be considered in the diagnostic algorithm of pediatric high-grade diffuse gliomas. H3: Histone-3, IDH: isocitrate dehydrogenase, * These types of tumors do not have an established CNS WHO grade yet.

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