EGF and neoplasm: Further work demonstrated the presence of a paracrine loop in which breast cancer cells recruit macrophages by producing colony stimulating factor‐1 (CSF‐1), and macrophages promote tumor cell invasiveness by producing epidermal growth factor (EGF)62, 63, 64 These studies set the stage for extensive additional work on the variety of functions of macrophages in the growth, metastasis, and response to therapy in breast and other tumor types.65, 66, 67, 68, 69, 70