Characterization of High-Grade Glial and Related Neuroepithelial Tumors Using the AOSNP-ADAPTR Framework: A Case Series With Review of Literature.

High-grade glial tumors are among the most aggressive primary neoplasms of the central nervous system and are associated with substantial morbidity, rapid progression, and poor survival. The classification of high-grade glial tumors requires a diagnostic approach combining histomorphology with immunohistochemical and molecular findings. In resource-constrained settings, the AOSNP-ADAPTR (Asian Oceanian Society of Neuropathology - Adapting Diagnostic Approaches for Practical Taxonomy in Resource-Restrained Regions) framework provides a practical strategy for implementing these principles using available diagnostic tools. This case series included five adult patients with intracranial tumors showing high-grade glial or related neuroepithelial morphology on histopathological examination. Clinical presentation, radiological findings, gross features, microscopic morphology, and available immunohistochemical findings were evaluated. Markers used or recommended included GFAP, Olig2, S-100, IDH1 R132H, p53, ATRX, Ki-67, EMA, D2-40, CD56, and cytokeratin markers, wherever indicated. Some immunohistochemistry (IHC) images included in this manuscript were obtained from an external referral laboratory because the corresponding IHC markers were not available at our institute. Consequently, these images contain the original laboratory watermark and have been retained in their original form to preserve image authenticity. All five patients were male, with ages ranging from 45 to 84 years. The common presenting features included headache, seizures, focal neurological deficits, lethargy, and symptoms of raised intracranial pressure. Four cases showed histomorphological features consistent with a diffuse high-grade glial neoplasm with necrosis and microvascular proliferation. Among these, three cases were in keeping with glioblastoma-like morphology, while one IDH1 R132H-positive tumor required integrated interpretation under the fifth edition of the WHO Classification of Central Nervous System Tumors (WHO CNS5) terminology and was appropriately classified as astrocytoma, IDH-mutant, CNS WHO grade 4 rather than glioblastoma. One additional case showed perivascular pseudorosettes and ependymal canal-like structures, raising the possibility of a high-grade ependymal or glial neoplasm and warranting further immunohistochemical categorization. The cases illustrated the diagnostic utility of combining histopathology with a targeted IHC panel in a resource-adapted setting. This case series demonstrates the clinicopathological and immunohistochemical spectrum of high-grade glial and related neuroepithelial tumors. IDH1 R132H IHC was critical in reclassifying one morphologically grade 4 tumor as an astrocytoma, IDH-mutant rather than a glioblastoma. Aberrant CK7 expression in one case highlighted the need for expanded IHC to exclude metastatic carcinoma. The AOSNP-ADAPTR framework enables WHO CNS5-aligned classification using targeted IHC panels in resource-constrained settings.