10260- MPC-25 INTEGRATED DIAGNOSIS OF GLIOMA IN KYOTO UNIVERSITY HOSPITAL

Abstract In 2021, WHO classification of tumours of the central nervous system (CNS) was published, which drastically changed the diagnostic approach of the tumors in the CNS. Although the latest classification has gradually become more widespread, it is still not easy to search for genetic mutations at many institutions in Japan, including Kyoto University Hospital (KUHP), and this remains an obstacle to the use of the above classification. At the 40th Brain Tumor Society Meeting held in 2022, we introduced our efforts in the diagnosis of glioma, including: (1) holding preoperative/postoperative clinical, imaging, and pathology conferences, (2) consultation to Kansai Molecular Diagnosis Network for CNS Tumors, (3) submission of specimens for cancer gene panel testing for insurance purposes, and (4) external consultation, DKFZ classification by methylation array analysis, and comprehensive analysis using next-generation sequencers. In our hospital during the 3 years from 2021 to 2023, approximately 140 cases of glioma including recurrence were diagnosed. The results of IDH1 R132H and H3K27M immunostaining and genetic abnormalities were consistent in all cases. On the other hand, some gliomas that were IDH1 R132H negative by immunostaining were reclassified as glioblastoma (n=13) or IDH2 mutant astrocytoma (n=1) based on molecular pathological findings, meaning that the diagnosis obtained from the initial pathological diagnosis may not be the correct one based on the molecular pathological findings. One case could not be classified even after performing (2)-(4) above, and one was found to have novel genetic abnormalities. As many medical institutions face difficulties in brain tumor classification based on the latest WHO classification, we would like to share our approach in this presentation and contribute to the improvement of brain tumor pathology diagnosis in Japan.