Molecular Reclassification of Diffuse Gliomas: A Feasibility Study of Clinical Features and Survival Outcomes in Colombia

Background/Objectives: The 2021 World Health Organization Classification of Tumors of the Central Nervous System (WHO CNS5) integrates histological and molecular criteria for adult diffuse gliomas, but comprehensive molecular testing may be difficult to implement in resource-limited settings. This study assessed the feasibility of a sequential, marker-based approach for diagnostic reassessment and described its association with clinical characteristics and overall survival (OS) in adults from Colombia. Methods: We retrospectively analyzed 68 adults with diffuse gliomas treated at two referral hospitals in Bogotá, Colombia, between 2015 and 2023. Molecular assessment used IHC, FISH, PCR, and Sanger sequencing according to the available tissue and diagnostic workflow. The study did not include comprehensive NGS or systematic assessment of combined whole-chromosome 7 gain/chromosome 10 loss (+7/−10). Results: The diagnosis changed after molecular reassessment in 51.5% of cases. The proportion classified as glioblastoma increased from 48.5% under the historical histologic classification to 66.2% under the WHO CNS5-based algorithm, whereas FISH-defined oligodendrogliomas decreased from 17.6% to 11.8%. OS differed among historical histologic groups (p = 0.03), but not among the WHO CNS5-based groups (p = 0.13). Female sex was associated with longer OS in unadjusted analysis (p = 0.02), while age was the only independent predictor in the multivariable analysis. Conclusions: Sequential molecular reassessment materially changed diagnostic categorization in this cohort and was feasible using locally available marker-based methods. However, the results are exploratory, limited by small molecular subgroups, incomplete molecular coverage, and the retrospective treatment context; they should not be interpreted as demonstrating improved treatment selection or survival after reclassification.