FLT1 and neoplasm: We analyzed the expression of endothelial markers (EGFL7, FLT1, PTPRB33), mesenchymal cells (COL1A2, COL1A1, PDGFRB34,35) and immune markers (ITGAM, CD247, PTPRC36–38) in MYCN-amplified neuroblastoma patient samples (with at least 90% tumor purity) and tumors from Protocol #4.