For total CRC, MLH1 promoter methylation was detected in 62.6% (95% CI: 54.0–70.4%) of the 968 MSI-H CRC in 12 studies, 12.2% (95% CI: 3.0–38.2%) of the 344 MSI-L CRC in four studies, 55.8% (95% CI: 45.2–65.8%) of the 1325 MSI CRC in 16 studies, and 5.2% (95% CI: 2.2–11.6%) of the 1791 MSS CRC in 10 studies (P<0.001), respectively (Table 2). This evidence concerns the gene MLH1 and colorectal carcinoma.