Aims Although much data have accumulated on sessile serrated adenoma/polyp/lesion (SSA/P/L) in general, its characteristics in specified contexts are less well elucidated. This lack of knowledge is even more conspicuous concerning its borderline counterpart, referred to as BSSA/P/L. The previous histological observations of the authors on SSA/P/L and BSSA/P/L in general are here extended to encompass attributes of these polyps in the context of synchronous colorectal carcinoma (SCRC), with a focus on the place of BSSA/P/L in the spectrum of non-dysplastic serrated polyps.

Methods 219 SSA/P/Ls, 206 BSSA/P/Ls and 170 hyperplastic polyps (HPs) were examined for SCRC. Demographics, polyp details (size, site, BRAF ^(V600E)) and advanced synchronous conventional adenomas were recorded.

Results SCRC was present in 12.3% of SSA/P/Ls, 7.1% of HPs (p=0.09) and 8.3% of BSSA/P/Ls. Patients' ages were comparable. Gender distribution of SSA/P/L and BSSA/P/L was equal, which differed, albeit insignificantly, from a male predominance of HPs. More SSA/P/Ls and BSSA/P/Ls than HPs exceeded 4 mm (p≤0.0001). A proximal site characterised SSA/P/L compared with BBSA/P/L and HP (p<0.0001). BRAF mutation was more prevalent in SSA/P/Ls and BSSA/P/Ls, which further coexisted with advanced synchronous conventional adenomas less commonly than HPs.

Conclusions BSSA/P/L was like SSA/P/L in most respects. The lower SCRC prevalence of BSSA/P/L could fit the idea of BSSA/P/L as a precursor to SSA/P/L, a notion that deserves attention when formulating guidelines for CRC screening.