The inflammatory microenvironment in screen-detected premaligant adenomatous polyps: early results from the...

Around 40% of patients who attend colonoscopy following a positive stool screening test have adenomatous polyps. Identifying which patients have a higher propensity for malignant transformation is currently poorly understood. The aim of the present study was to assess whether the type and intensity of inflammatory infiltrate differ between screen-detected adenomas with high-grade dysplasia (HGD) and low-grade dysplasia (LGD).

A representative sample of 207 polyps from 134 individuals were included from a database of all patients with adenomas detected through the first round of the Scottish Bowel Screening Programme in NHS Greater Glasgow and Clyde (April 2009-April 2011). Inflammatory cell phenotype infiltrate was assessed by immunohistochemistry for CD3+, CD8+, CD45+ and CD68+ in a semi-quantitative manner at 20× resolution. Immune-cell infiltrate was graded as absent, weak, moderate or strong. Patient and polyp characteristics and inflammatory infiltrate were then compared between HGD and LGD polyps.

CD3+ infiltrate was significantly higher in HGD polyps compared to LGD polyps (74 vs. 69%; P < 0.05). CD8+ infiltrate was significantly higher in HGD polyps compared to LGD polyps (36 vs. 13%; P < 0.001) whereas CD45+ infiltrate was not significantly different (69 vs. 64%; P = 0.401). There was no significant difference in CD68+ infiltrate (P = 0.540) or total inflammatory cell infiltrate (calculated from CD3+ and CD68+) (P = 0.226).

This study reports an increase in CD3+ and CD8+ infiltrate in HGD colonic adenomas when compared to LGD adenomas. It may therefore have a use in the prognostic stratification and treatment of dysplastic polyps.