To mimic conditions occurring in breast tumor-bearing obese patients/experimental animals (i.e., adverse activation of Mφ [35,41] due to the presence of increased concentrations of sFA in circulation [36]), murine and human (i.e., E0771, MCF7) ER + BC cell lines were incubated with medium conditioned by primary Mφ (isolated as described in Methods), either unstimulated or stimulated by SFA (i.e., palmitate, dominant SFA present in fat depots/circulation of female patients [70] and responsible for adverse Mφ activation under obese conditions [35,37,39,71]. This evidence concerns the gene ESR1 and breast cancer.