They are different from terminally differentiated tumor-associated macrophages (TAMs), identified as Mac-1 (CD11b) and F4/80+, which have been shown to promote tumor progression and metastasis through elevated CSF-1 production and enhanced epidermal growth factor (EGF) signaling in cancer cells.(24) Similarities between TAMs and these immature myeloid cells were noticed from profiling work,(25) but differences between the two populations also were evident. This evidence concerns the gene CSF1 and neoplasm.