The Price of Precision: A Critical Review of Molecular Diagnostics in Glioma, From Guidelines to Global Disparities

Gliomas have undergone a profound redefinition over the past decade, transitioning from morphology-based entities to biologically coherent diseases defined by molecular alterations. The 2021 WHO Classification of Tumors of the Central Nervous System and its 2022 update formalize this shift, establishing integrated diagnosis as the global standard and identifying essential biomarkers—including IDH mutations, 1p/19q codeletion, ATRX loss, TP53 mutation, TERT promoter mutation, EGFR amplification, and +7/−10 cytogenetics—that shape prognosis, therapeutic decision-making, and clinical trial eligibility. In this review, we synthesize the current molecular taxonomy of gliomas and compare recommendations from major international guidelines (WHO, NCCN, EANO) and the Italian Association of Neuro-Oncology (AINO). Recognizing that contemporary practice employs a complementary, purpose-driven array of diagnostic modalities—from immunohistochemistry and PCR-based methods to next-generation sequencing and DNA methylation profiling—we critically examine the profound global disparities that hinder implementation, focusing on economic constraints, infrastructural limitations, regulatory barriers, and workforce shortages. By integrating health-economic evidence, we demonstrate that the societal and financial burden of non-implementation far exceeds the investment required for molecular testing. We propose a tiered implementation framework in which clinically actionable information is obtainable for most glioma patients through accessible, cost-effective technologies, with more resource-intensive modalities reserved for specific clinical scenarios. Ensuring equitable access to integrated diagnostics, defined as the right test for the right clinical question, is essential not only for precision neuro-oncology but also for global healthcare justice and scientific progress.