The mechanism of CYP1A1 gene polymorphism effect on cancer induction can be attributed to different pathways such as phase 1 bioactivation of xenobiotics and involvement in the metabolisms of estrogen (converting the metabolites into carcinogens) that leads to elevating the risk of breast cancer (17), lung cancer (29, 30), and renal cell cancer (39), or due to the activation of mammary carcinogens by tobacco metabolites (40). The gene discussed is CYP1A1; the disease is breast cancer.