To evaluate intra-tumoral heterogeneity, sections of the TMA were stained simultaneously with antibodies against the leukocyte marker CD45 to demarcate the tumor-immune microenvironment (TIME), the epithelial cell marker PanCK to mark the tumor cores (L and LB), GFAP (glial fibrillary acidic protein) to identify the tumor brain microenvironment (TBME), and SYTO83 to mark the cell nuclei (Fig. 1a). The gene discussed is GFAP; the disease is neoplasm.