EGFR and astrocytoma (excluding glioblastoma): According to the WHO 2021 classification schema, GBM is currently defined as diffuse, grade 4, astrocytoma lacking isocitrate dehydrogenase 1 gene (IDH) and histone mutations that have concomitant +7/−10, epidermal growth factor receptor gene (EGFR) amplification, telomerase reverse transcriptase (TERT) promoter mutations, mitoses, necrosis, or microvascular proliferation [1,2,3].