PMS1 and hereditary nonpolyposis colon cancer: Although the majority of the patients in our group do not appear to have classical HNPCC, the role of alternative MMR genes such as MSH6, PMS1, PMS2, MLH3 and EXO1 should be considered (Akiyama et al, 1997; Miyaki et al, 1997; Thompson et al, 2004).