MTHFR and breast cancer: As presented in Table 5, our data suggested the haplotype composed of the 2 alternative alleles of MTHFR SNPs (rs1801133/T - rs1801131/C) was strongly associated with early age at diagnosis of BC (15.4% of early onset BC vs. 5.1% diagnosed after 40 years; OR: 3.52, 95% CI: 1.23–10.06, p = 0.02).