IDH1 and central nervous system cancer: It is intriguing that dedifferentiated chondrosarcoma carry an isocitrate dehydrogenase-1 (IDH1) and isocitrate dehydrogenase-2 (IDH2) mutation (37) with higher frequency than conventional chondrosarcoma since in glioma the neoantigens derived from IDH-mutation have been shown to induce a cellular immune response (38–42).