MRC1 and cancer: The most frequently observed cancer is colorectal cancer (2942 tumours in 2519 MMR PV carriers), followed by endometrial cancer (836 tumours in 833 MMR PV carriers), Upper GI cancers (279 tumours in 265 MMR PV carriers) and urinary tract cancers (249 tumours in 215 MMR PV carriers) (Supplementary Table 5).