MRC1 and osteosarcoma: Analysis of 88 osteosarcoma tissue samples from the GDC data portal revealed elevated CD14 and CD68 levels (macrophage markers) as well as the presence of CD163 and CD206 (M2 macrophage markers); however, M1 macrophage markers (CD80, iNOS and IL-1β) were not detected (Fig. 1A).