ERBB2 and neoplasm: In the Her2+ 4T1 murine breast tumor model we find two distinct subsets of immature myeloid-derived suppressor cells (MDSCs) based on Ly6G or Ly6C expression, i.e., CD11b+Ly6G+Ly6Clow granulocytic (G)-MDSCs and CD11b+Ly6G−Ly6Chigh monocytic (M)-MDSCs, in the spleen as the tumor progresses9.