MTHFR and polyp of large intestine: As a genetic effect of MTHFR rs1801133 and rs1801131 polymorphisms has been suggested in the susceptibility to colorectal cancer [6, 11, 33, 34], additional confounding factors such as smoking, drinking, age, sex, and patient features should be adjusted for further investigation of the MTHFR variants in the malignant conversion from colorectal polyp.