Sessile Serrated Polyps Without Dysplasia Thrives With Asymmetric Relocation of Cell Proliferation-domains.

Background/Aim: Sessile serrated polyps without dysplasia (SSPND) are characterized by crypts with serrated epithelium, albeit with irregular, corrupted shapes (CCS). Patients and Methods: Cell proliferation was explored in the CCS from 60 SSPND and in the crypts from 12 normal colons. Sections were immuno-stained with the Ki-67 proliferation-cell (PC) marker, and with the p53 tumour-suppressor gene. Results: Three predominant PC-phenotypes were found in the CCS from the 60 SSPND: 44 (73.3%) exhibited ectopic, asymmetric, randomly distributed PC-clusters, 12 (20.0%), continuous PC in one or in both slopes of the crypts, and in the remaining 4 (6.7%), single, randomly distributed PC were recorded. In contrast, the scrutiny of more than 200,000 normal colon crypts (controls) showed symmetrically aligned PC, restricted to the lower third of the crypts. p53-up-regulation in CCS was recorded in 11(18.3%) of the 60 NDSSP, but in none of the normal crypts in the 12 controls. Conclusion: The non-dysplastic epithelium that lines CCS in SSPND coexists with an asymmetric relocation of the PC-domains. In addition, the CCS in nearly one-fifth of the SSPND exhibited p53-upregulated cells. Taken together, the non-dysplastic CCS epithelium in SSPND thrives with somatic mutations. The accretion of putative mutated non-dysplastic CCS might be a crucial event in the evolution of colonic SSPND towards sessile serrated adenomas.