Difference between hyperplastic polyp traditional serrated adenoma and sessile serrated adenoma
• HPs are characterized by serrated crypt lumens that are lined by colonic epithelial cells that lack dysplasia
TSAs are polyps that show serrated crypt lumens with stratified pencil-like nuclei at the base of crypts that resemble the ones seen in tubular adenoma. Some authors have described ectopic crypt formation in TSA. These are short crypts away from muscularis mucosae and are considered precursors to colorectal cancer (CRC).
•SSAs are seen more on the right side of the colon in older adult women, and are always sessile. A few (10%) may occur in the left colon. In various studies, these account for 4% to 15% of serrated polyps. Architecturally, it differs and shows serrated lumens with a horizontal, broad or boat-shaped base. The lining epithelium is variable and shows goblet or mucinous cells or may be mucin depleted, and may show nuclear stratification. A subset of these polyps may show focal conventional dysplasia; however, architecture is the key finding. This adenoma has been associated with microsatellite instability–high (MSI-H)–related sporadic CRCs (hypermethylation of promoter gene). The majority of these show BRAF mutation, and approximately 1 in 25 (4%) of these may progress to cancer.
Mixed polyps are HPs with typical adenoma foci.