The data from human and in vivo studies, as well as in vitro experiments suggest that exposure to environmental pollutants especially PAHs and dioxin-like chemicals, potent ligands for AhR, increases breast cancer risk and worsens outcome through chemoresistance, immune evasion, EMT, tumor cell proliferation, and metastasis, linked functional outcomes of cancer stemness (Figure 2). This evidence concerns the gene AHR and breast cancer.