CD19 and neoplasm: Given that CEBPB and CSF1R play essential roles in defining macrophage fate13,17 and that the biphenotypic B-cell progenitors and B1 B cells can generate macrophages in mice15,18, we tested whether cancer induces the macrophage-like cells from pre-B cells by FACS evaluating tumor-infiltrating CD19+ B cells (TIB) and macrophages (TAM, based on F4/80+CD11b+)19 in B-cell sufficient (WT) and deficient BALB/c mice (μMT, where B cells do not differentiate beyond pro-B cells20) with 4T1.2 cancer.