MLH1 and hereditary nonpolyposis colon cancer: Caution is required, however, since the absence of germline mono-allelic promoter hypermethylation in this study may have been due to the limited number of patients analyzed and Hitchins et al. reported a very low incidence of germline mono-allelic hypermethylation of the MLH1 promoter in HNPCC (1 out of 160 HNPCC candidates) [19], it is impossible to rule out the possibility that analysis of a larger number of gastric cancer patients would reveal cases with germline mono-allelic hypermethylation of the CDH1 promoter.