IDH1 and astrocytoma (excluding glioblastoma): In addition, given that the isocitrate dehydrogenase 1 (IDH1) mutation has been found to be an essential genetic aberration in grade II–III diffusely infiltrating astrocytomas and especially in secondary GBMs[14, 15], we wanted to study whether this stem cell marker, polySia-NCAM, can be of additional help in identifying the prognostic characteristics if grade II-IV astrocytomas and secondary GBMs with and without IDH1 mutations.