Differences in T-cell Densities and Neighborhood Patterns in Human Colorectal Adenomas and Sessile Serrated Lesions

T-cell responses influence recurrence and survival in colorectal cancer. T-cell subset distributions vary by molecular phenotype and anatomic location, shaping cytotoxic or immune-cold tumor immune microenvironments. However, the T-cell contexture and their spatial proximities within preinvasive lesions are not well characterized.

We analyzed sessile serrated lesions (SSL), tubulovillous/villous adenomas (TV), and tubular adenomas (TA) from 3 studies (N = 120). Whole-slide multiplex immunofluorescence was used to quantify 8 T-cell subsets [CD4+, CD8+, helper T (Th) 1 (CD4+TBX21+), Th17 (CD4+RORC+), regulatory T cells (Treg; CD4+FOXP3+), Tc1 (CD8+TBX21+), Tc17 (CD8+RORC+), and TcTreg (CD8+FOXP3+)]. Densities were compared by histology using a generalized linear mixed model with a negative binomial distribution, including an offset for total cell area and adjusting for age, sex, anatomic location, and lesion size. Nearest neighbor (NN) analyses assessed spatial proximities of T-cell pairs across lesion types.

TAs and SSLs had higher CD4+ and CD8+ T-cell densities than TVs (q <0.05). Compared with TVs, TAs also had higher Th17 cell densities, whereas SSLs showed a trend toward lower Treg densities (q = 0.06). NN analysis showed greater Treg clustering in TVs than in SSLs and TAs. In contrast, TA versus SSL comparisons demonstrated predominant CD4+ clustering with Th17, Th1, and CD8+ subsets.

TVs exhibited lower T-cell densities and greater Treg clustering, consistent with an immune-cold environment. SSLs and TAs were more immune-infiltrated than TVs, but TAs had higher inflammation and CD4+-dominant clustering, suggesting stronger helper coordination.

Preinvasive lesions demonstrate immune and spatial heterogeneity which may have implications for primary or secondary prevention.