MTHFR and diabetes mellitus: Therefore, we conducted a stratified analysis on data according to age, diabetes mellitus, presence of hypertension, family history of cancer, menopause, body mass index (BMI), tumor site, tumor size, and lymph node metastasis (LNM) stage to determine whether the MTHFR C677T polymorphism is associated with BC incidence in specific subtypes of the study population, as shown in Table 1.