Sessile serrated polyps of the colorectum are rare in patients with Lynch syndrome and in familial colorectal cancer families

Whereas the generally accepted carcinogenesis pathway of the microsatellite instabile high (MSI-H) colorectal carcinoma (CRC) involves the traditional adenoma in patients with Lynch syndrome, a serrate pathway involving serrate adenomas (SA) and sessile serrate polyps (SSP) characterize the sporadic MSI-H counterpart. Recent studies have, however, challenged such simple one-pathway models, inviting the consideration of alternative, unexpected pathways. Here, the issue as to the possible role of SSP, primarily in the context of Lynch syndrome, but also in subjects from familial CRC families (FCF) is addressed. Polyps coded as hyperplastic polyps (HP) from subjects with Lynch syndrome and FCF enrolled in the HNPCC-register at the Hvidovre University Hospital as well as adenomas from this population were retrieved and reviewed for features of SSP. Ninety-eight polyps coded as HP and 41 polyps coded as adenoma from 14 individuals with Lynch syndrome as well as 17 individuals from FCF constituted the study material. Seven of the 98 polyps coded as HP displayed histological features that, to varying extent, deviated from the traditional HP (THP), yet, merely two of these, both from the FCF, were considered examples of probable SSP. None of the 41 cases coded as adenoma possessed a morphology that qualified as SSP. The prevalence of SSP was not increased as compared to the background population and thus, this serrated lesion does not appear to play a tumorigenic role in Lynch syndrome, nor in FCF.