IDH1 and glioblastoma: In terms of the nomenclature and grading of common adult-type diffuse astrocytic gliomas, the 2016 World Health Organization (WHO) Classification of Tumors of the Central Nervous System (CNS) assigned isocitrate dehydrogenase (IDH)-mutant diffuse astrocytic tumors to three different tumor types (diffuse astrocytoma, anaplastic astrocytoma, and glioblastoma) depending on histologic parameters and immunohistochemical features [1].