According to the 2021 World Health Organization (WHO) classification of tumors of the CNS, GBM is diagnosed based on the presence of necrosis, microvascular proliferation, and 1 or more of 3 specific genetic parameters [telomerase reverse transcriptase (TERT) promoter mutation, epidermal growth factor receptor (EGFR) gene amplification, combined gain of chromosome 7 and loss of chromosome 10 (+7/-10)] with wild-type forms of isocitrate dehydrogenase (IDH) 1/2 (3). The gene discussed is EGFR; the disease is central nervous system neoplasm.