CD34 and central nervous system cancer: Moreover, there was no correlation between the densities of rounded CD34+ cells and PpIX+ cells (Figure 4G; slope = slope = 0.01 ± 0.02, R2 = 0.06, P = .61, n = 8 IDH1mut gliomas), suggesting the activated microglia were not major contributors to the PpIX signal.