SDC2 and colorectal carcinoma: Accumulated evidence shows that epigenetic gene regulation is closely related to tumourigenesis, and it has been reported that the positive detection rate of the mSDC2 test in different age groups ranged from 2.2% to 29.7%, and showed a trend for increasing relationship between the methylation rate of the SDC2 gene and the PPV value for CRC, especially in the population above 50 years of age.