Correlation of tumor grade with increased CD3+ t-cell and FOXP3+ regulatory T-cell infiltration in neuroendocrine neoplasms.

Abstract

e15186 Background: Neuroendocrine neoplasms (NENs) comprise a biologically heterogenous group of malignancies with diverse clinical behavior and outcomes. Tumor grade, defined by proliferative indices such as Ki-67, is a key determinant of prognosis and therapeutic decision-making across NEN subtypes. 1 Increasing evidence suggests that the tumor microenvironment (TME) influences tumor progression and treatment response. 2 Tumor-infiltrating CD3+cells mediate anti-tumor immunity, whereas FOXP3+ T-regulatory cells suppress effector T-cell activity and promote immune evasion. 3 While prior studies of the neuroendocrine tumor microenvironment have largely been limited to single organ systems, our study evaluates immune infiltration across a multi-site cohort of neuroendocrine neoplasms, enabling direct comparison of immune features by tumor grade. 4,5 We asked whether immune cell infiltration of high-grade NENs differs from low-grade NENs. Methods: We conducted a retrospective cohort study using archived, deidentified NEN specimens from Fox Chase Cancer Center. A tissue microarray comprising 19 low-grade (grades 1 and 2) and 19 high-grade (grade 3) NENs from multiple primary sites, including the gastrointestinal tract, pancreas, lung, bladder, ovary, and breast, was analyzed. Tumors were graded according to the World Health Organization criteria based on Ki-67 labeling index and mitotic rate. Immunohistochemical staining was performed for CD3 and FOXP3. Immune cell infiltration was quantified using AI-assisted digital image analysis (Visiopharm), with marker-positive cells normalized to the analyzed region of interest and expressed as a cell density (cells/mm 2 ). For cases with multiple tissue cores, density values were averaged to generate a single tumor-level value. Group comparisons were performed using two-sample Welch t-tests. All tests were two-sided, with p < 0.05 considered statistically significant. Results: Immune cell infiltration differed significantly by tumor grade. G3 NENs demonstrated higher CD3+ T-cell density compared with G1/2 NENs (421.82 vs 132.22/mm 2 , p = 0.046). FOXP3+ T-reg density was also increased in G3 NENs (48.89 vs 9.95 cells/mm 2 , p = 0.029). Conclusions: High-grade neuroendocrine neoplasms exhibit increased infiltration of both CD3+ T-cells and FOXP3+ regulatory T-cells compared with low-grade tumors, suggesting a more immune-infiltrated yet potentially immunosuppressive tumor microenvironment with increasing tumor grade. These findings highlight tumor grade as correlate of immune microenvironment features in NENs and may have implications of immunotherapeutic strategies. Immune Cell Infiltration by Tumor Grade in Neuroendocrine Neoplasms. Mean CD3+cells/mm 2 Mean FOXP3+ cells/mm 2 High Grade 421.82 48.89 Low Grade 132.33 9.95 P-Value 0.046 0.029