B2M and neoplasm: Similar proportions of the B2M‐mutant and B2M‐wild‐type dMMR tumours were T4 stage [18% (seven of 38) versus 19% (14 of 74)], poorly differentiated [16% (six of 38) versus 19% (14 of 74)], mucinous [26% (10 of 38) versus 28% (21 of 74)], had KRAS mutations [25% (nine of 36) versus 25% (18 of 73)], BRAF mutations [33% (12 of 36) versus 28% (21 of 74)] and high oncotype DX recurrence scores [28% (10 of 36) versus 27% (17 of 62)].