Disturbed homocysteine metabolism caused by genetic (mainly mutations and polymorphisms) and epigenetic alterations of the genes (MTHFR, CBS, MTRR, MTR, MTHFD, BHMT, TYMS and TCN 2), involved in homocysteine metabolism, has been found in many solid tumors including CRC [299]. Here, TYMS is linked to colorectal carcinoma.