CCR2 and neoplasm: Tumor-specific subtypes as revealed by single-cell technology include early immigrant macrophages (HLA-DR+CD192+), monocyte resembling immature macrophages (CCR2+), tissue-resident macrophages (CD206+HLA-DR+), TAMs (CD64+HLA-DR+), and myeloid-derived suppressor cells (MDSC; HLA-DR−/low) (19, 44) (Figure 2).