PTPRC and cancer: However, some WBCs have low or absent expression of CD45 such as neutrophils, myeloid‐derived suppressor cells (MDSCs), or other immature myeloid subsets.32 To identify these CD45low/− WBCs, we chose CD11b, a myeloid‐specific marker which is highly expressed at an early stage of myeloid development and strongly expressed on CD45low myeloid derivatives, including both MDSCs and neutrophils.33 More importantly, some mature myeloid derivatives like neutrophils, which express the low levels of CD45 increase in patients with progressive cancer, and stain positive for CK.