No more hide and seek

Large non-pedunculated colorectal polyps and the occurrence of post-colonoscopy colorectal cancer are the subjects of the thesis “No more hide and seek”. The thesis shows that non-pedunculated colorectal cancers consist of a morphologically heterogeneous group (a group with high variety in tissue characteristics), with a different risk of cancer cells at diagnosis for each subtype. Accurate prior assessment of this risk could prevent suboptimal treatment. Furthermore, this thesis shows that patients with large flat polyps develop more polyps in the future than patients with other polyp types. Flat polyps are harder to detect than other polyps. It is suggested that they can be more easily missed during colonoscopy with the risk of malignant transformation afterwards, which should be prevented by colonoscopy. This could result in the occurrence of so-called post-colonoscopy colorectal cancer. Faster growth by different mutations was hypothesized as another factor in post-colonoscopy colorectal cancer occurrence. This thesis examined the genetic profile of post-colonoscopy colorectal cancers in comparison with common colorectal cancer. The results showed no unique mutations in post-colonoscopy colorectal cancers, but they did show more often the features as seen in a more subtle and flat category of flat bowel polyps. Improvements in detection of these polyps remain important in post-colonoscopy colorectal cancer prevention.