We observed that the MTHFR A1298C (rs1801131) polymorphism reduced the risk of developing breast cancer in the codominant model (genotype CC - OR: 0.22; 95% CI: 0.06-0.74; p=0.014), recessive model (OR: 0.22; 95% CI: 0.07-0.76; p=0.004), and log-additive model (OR: 0.70; 95% CI: 0.49-0.98; p=0.035). The gene discussed is MTHFR; the disease is breast cancer.