A common single nucleotide polymorphism (SNP), A1298C/rs1801131 A/C, is located in the coding carboxy-terminal regulatory region domain [7] and lymphocytes from individuals containing 1298CC genotype have been found to have approximately 60% of wild-type in vitro MTHFR activity [8], which acts as a risk factor in cancer development. Here, MTHFR is linked to cancer.