Tissue sample preparation for immunohistochemical evaluation was carried out in the Histology and Tissue Analysis Core at Dell Pediatric Research Institute (DPRI) at The University of Texas at Austin. The formalin-fixed tumor tissues were embedded in paraffin wax, sectioned, and stained with an antibody against CD-31 (Abcam, Cambridge, MA, USA) as a marker for angiogenesis (n = 3) 41 (link). Slides were then scanned, and images were taken using the ScanScope XT (Aperio Technologies, Vista, CA, USA).