Our study further suggests that somatic MMR mutations are more common than germline mutations in PCas, and that inactivation of MSH2 and MSH6 appears to be the main cause of MSI in PCas, in contrast to colorectal and endometrial cancer, where MSI is most often due to epigenetic silencing of MLH1 (11, 12). Here, MLH1 is linked to endometrial cancer.