PTPRC and breast neoplasm: In MMTV-PyVT breast tumor tissue, two major tumor-infiltrating myeloid cell populations were identified: CD45+CD11b+Gr1hiF4/80− (Gr1+F4/80−, tiMDSC) and CD45+CD11b+Gr1−F4/80+ (Gr1−F4/80+, TAM) (Figure 1A and Supplementary Figure 1).