ESR1 and breast cancer: In two separate studies this analysis revealed strong significant correlation of the SNPs of (TC+TT) of MTHFR C677T in one study and that of (AC+CC) of MTHFR A1298C in the other study versus each of the BC clinicopathological data including: dual negativity of ER and PR, high HER2neu expression, involvement of cancer in lymph nodes and advanced tumor stage (III-IV) and bigger size (T2-T3) giving highly significant P values (0.001).