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). The gene discussed is EXO1; the disease is hereditary nonpolyposis colon cancer.