Abstract IA05: The serrated pathway of colorectal tumorigenesis

Over last 15 years it has been recognized that a significant proportion of colorectal cancers arise from serrated polyps, previously called hyperplastic polyps that were thought to be of no malignant potential. Minimum estimates of the proportion are based on the presence of the BRAFV600E mutation since this only occurs in serrated polyps. In a series of cancers occurring between 1998 and 2007 13% had a BRAFV600E mutation whereas this proportion was 20% in our recent series from 2012 to 2013 (1). The proportion may be increasing since serrated pathway cancers are predominantly proximal and the rate of decline in incidence is less in proximal than distal cancers.The WHO classification of serrated lesions now recognizes hyperplastic polyps (HP), sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA). SSAs and TSAs are premalignant but do not have conventional dysplasia. TSAs are rare but easily detected lesions mostly in the distal bowel with 20% having advanced dysplasia or invasive malignancy (2). By contrast, SSAs are common constituting 12% of all polyps (3) and are typically pale, sessile lesions with indistinct borders. More than 70% occur in the proximal colon and they are more common in females. Until very recently they were often missed or incompletely resected by colonoscopists and were underdiagnosed by pathologists. For these reasons, they have contributed disproportionately to the failure of colonoscopy to fully protect against cancer. The natural ...
Source: Cancer Research - Category: Cancer & Oncology Authors: Tags: Understanding the Origins of Colorectal Neoplasia Source Type: research