While mutations within the IDH-1/-2 genes can be found in more than 70 % of all primary astrocytomas (WHO grades II/III), oligodendrogliomas, and secondary glioblastomas, the respective mutation rate is only about 5 % in primary glioblastomas and mutations within IDH-1/-2 are associated with positive clinical prognosis in astrocytoma and glioblastoma (Yan et al. 2009; Combs et al. 2011). Here, IDH1 is linked to astrocytoma (excluding glioblastoma).