IDH1 and astrocytoma (excluding glioblastoma): Further, specific heterozygous somatic point mutations of the isocitrate dehydrogenase gene (IDH1/2) were found in more than three-fourths of all oligodendrogliomas and nearly three-fourths of all astrocytomas of WHO grades II and III [11–13] and in all 1p/19q codeleted gliomas [14].