Diseases of the colon and rectum
-
Colorectal cancers arise via cumulative genetic and molecular changes that cause mucosal instability, premalignant polyps, and malignant transformation. Distinct neoplastic pathways characterized by chromosomal instability, genetic mutation, and epigenetic methylation have been described, but their associated precursor polyps have not. This study analyzes characteristics of precursor polyps occurring within different molecular subtypes of sporadic colorectal cancer. ⋯ Patients with microsatellite unstable colorectal cancers demonstrate an increased serrated polyp-to-adenoma ratio compared with microsatellite stable cancers regardless of methylator status. Loss of microsatellite stability appears to be a key event in serrated polyp and cancer formation. An increased proportion of serrated polyps to adenomas discovered in patients on colonoscopy should arouse suspicion that cancers arising in these patients are probably microsatellite unstable.