MLH1 and colorectal cancer: Following the findings by Kane and colleagues [27] demonstrating MLH1 promoter methylation in colorectal tumor tissue, and the report of Gazzoli and colleagues in 2002 [28] demonstrating white blood cell (WBC) DNA methylation of the MLH1 promoter in a young man diagnosed with an MSI positive colon cancer, MLH1 methylation has been detected in circulating leucocytes (WBC) of a subset of patients with sporadic MSI positive colorectal cancers.