For the MTHFR C677T genotype, there were 20 cases of wild-type CC, 52 cases of heterozygous mutant CT and 38 cases of homozygous mutant TT in normal group, 25 cases of CC, 56 cases of CT and 35 cases of TT in CIN group, and 34 cases of CC, 70 cases of CT and 42 cases of TT in cancer group, respectively (Fig. 2a). Here, MTHFR is linked to cervical squamous intraepithelial neoplasia.