In total, MMR protein immunohistochemistry was performed in 714 cm of mucosa (626 cm large bowel, 88 cm small bowel) from carriers of a Lynch syndrome mutation and 144 cm (129 cm large bowel, 15 cm small bowel) from patients without a germline mutation in the respective MMR gene, including 62 cm of mucosa (49 cm large bowel, 13 cm small bowel) from patients with sporadic MSI-H colorectal cancer. This evidence concerns the gene MRC1 and Lynch syndrome.