IDH1 and glioma: Since TCGA samples of GBM contain perinecrotic as well as bulk tumor, while IDH-wt grade II/III gliomas (by definition) do not contain necrosis, we reasoned that differential protein expression noted between these sample sets would be due mostly to the presence of necrosis (and its associated biological events) and could be used to compare our results from 5-ALA targeted sampling of PN and BT samples.