For example, mutations of the gene encoding isocitrate dehydrogenase 1 (IDH1) are very common in low-grade astrocytomas, anaplastic astrocytomas, oligodendrogliomas, anaplastic oligodendrogliomas, and secondary glioblastomas but very rare in de novo glioblastoma [7, 8]. Here, IDH1 is linked to astrocytoma (excluding glioblastoma).