Serrated colorectal polyps and polyposis

Serrated polyps represent a heterogeneous group of lesions, some of which have well-documented malignant potential. The histological classification of serrated polyps has evolved over the last two decades to recognize three major subtypes: hyperplastic polyp, sessile serrated adenoma/polyp and traditional serrated adenoma. Sessile serrated adenoma/polyp remains under-diagnosed while it represents up to 25% of all serrated polyps and is the precursor lesion to colorectal carcinoma evolving though the serrated neoplasia pathway with BRAF mutation and CpG island methylator phenotype. Pathologists need to be aware of the World Health Organisation criteria to correctly diagnose each entity as patient management guidelines are based upon the use of this classification. Serrated polyposis is an under-recognized syndrome with unknown genetic cause conferring an increased risk of colorectal carcinoma. Pathologists have a pivotal role in identifying these patients who should undergo yearly surveillance colonoscopy.