IDH1 and neoplasm: Using DAPI stain as a marker for all nuclei and the antibody against mutated IDH1, we observed that tumor cells accounted for 60–75% of all cells in the solid portion of the tumor and significantly less (approximately 45%) in the infiltration zone, reflecting the higher percentage of constitutive CNS cells in the infiltration zone than in the solid portion of the tumor (Figure 3A).