MLH1 and colorectal cancer: No polyps carried mutations in the MMR gene hMLH1; however, deficient MMR in the setting of non-familial cases of colorectal cancer primarily occurs via methylation of hMLH1. 25, 26 Deficiency of the MMR genes is manifested in changes in the length of microsatellite repeat sequences, which can be detected in colon polyps by using a novel panel of long mononucleotide repeats.20 Only two polyps displayed MSI: PF18 (regressing) and PF19 (stable); therefore, no relationship between MSI status and growth could be determined (see online supplementary table S3).