The vascularendothelial cell population in the osteosarcoma lesion tissues exhibiteda PECAM1­(+), CDH5­(+) phenotype, whereas the macrophage populationwas predominantly of the M2 type, expressing CD163­(+) and MRC1­(+),consistent with the characteristics of the tumor immune microenvironment(Figure C). The gene discussed is MRC1; the disease is osteosarcoma.