MLH1 and colorectal carcinoma: In comparison, the three primary and two secondary MLH1 epimutation cases all showed MLH1 hypermethylation in blood and normal mucosa-derived DNA samples, whilst CRCs from other reference groups had no detectible methylation in blood or normal mucosa except for one sporadic MLH1 methylated CRC (age of CRC diagnosis = 78 years), which showed 3.8% methylation only in the distant normal mucosa but not in blood or adjacent normal mucosa.