The 2021 World Health Organization (WHO) classification of tumors of central nervous system (CNS) distinguished IDH-wildtype glioblastoma from IDH-mutant astrocytoma; however, cystic glioblastoma is not captured in this classification system or other commonly described molecular profiles (WHO Classification of Tumour Editorial Board, 2021). The gene discussed is IDH2; the disease is astrocytoma (excluding glioblastoma).