POU5F1 and central nervous system cancer: However, comparing the ALA+ and the ALA PALE regions with the ALA− we found a higher percentage of Sox2 and Oct4 positive cells, indicating that cells endowed with stemness and able to support the glioma growth were located also beyond the tumor mass, in the region defined by a vague 5-ALA fluorescence, that cannot be eliminated, during surgery, without the support of the fluorescent stain.