IDH1 and astrocytoma (excluding glioblastoma): 8/89 (9%) cases that showed positive staining for IDH1 on immunohistochemistry were designated as astrocytoma- IDH mutant (WHO grade 4) whereas 81/89 (91%) cases that were negative IDH1 immunostaining were designated as glioblastoma- IDH wildtype (WHO grade 4) in accordance with the current WHO classification of tumors of CNS (2021).