PTPRC and neoplasm: MDSCs (CD45+CD11b+ Gr-1+) are a diverse population of immature myeloid cells which can be separated into two main groups in murine tumor tissues: monocytic MDSCs (M-MDSCs, CD45+CD11b+Ly6G−Ly6C+) and polymorphonuclear MDSCs (PMN-MDSCs, CD45+CD11b+Ly6G+Ly6C−).