Differences in T-cell densities and neighborhood patterns in human colorectal adenomas and sessile serrated lesions

BACKGROUND: 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. METHODS: We analyzed sessile serrated lesions (SSLs), tubulovillous/villous adenomas (TVs), and tubular adenomas (TAs) from three studies (N=120). Whole-slide multiplex immunofluorescence was used to quantify eight T-cell subsets (CD4⁺, CD8⁺, Th1 (CD4+TBX21+), Th17 (CD4+RORC+), Treg (CD4+FOXP3+), Tc1 (CD8+TBX21+), Tc17 (CD8+RORC+), 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. RESULTS: 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. CONCLUSION: TVs exhibited lower T-cell densities and greater regulatory T-cell 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. IMPACT: Preinvasive lesions demonstrate immune and spatial heterogeneity which may have implications for primary or secondary prevention.