IDH1 and astrocytoma (excluding glioblastoma): In a study of 25 adults with GC, patients were found to have isocitrate dehydrogenase (IDH) mutant astrocytoma, IDH mutant and 1p/19q codeleted oligodendroglioma or IDH wild type glioblastoma (RTK1, classic, mesenchymal, or H3F3A-G34 mutant) (1).