Anushankari Pandian, Sangeetha Nagalingam
Introduction: Gastrointestinal malignancies are biologically heterogeneous and show variable immune responses across anatomical sites. Tumour-Infiltrating Lymphocytes (TIL) reflects host immune response within the tumour microenvironment and can be assessed on routine haematoxylin and eosin-stained sections. Aim: To evaluate stromal TIL score in primary gastrointestinal malignancies and assess its association with histopathological parameters. Materials and Methods: This single-centre cross-sectional study included 45 primary gastrointestinal malignant tumours diagnosed between January 2024 and December 2025 at Karpaga Vinayaga Institute of Medical Sciences and Research Centre, Chengalpattu, Tamil Nadu, India. Tumours from the stomach, colon, rectum, duodenum, and oesophagus/ gastro-oesophageal junction were included. Histopathological parameters including tumour site, histological subtype, tumour grade, lymphovascular invasion, perineural invasion, lymph node status, pathological tumour stage, and TNM stage were recorded. Stromal TIL score was assessed as the percentage of stromal area occupied by mononuclear inflammatory cells. For dichotomised analysis, cases with stromal TIL score >50% were classified as high-TIL, whereas cases with stromal TIL score ≤50% were grouped as low-TIL. Statistical Analysis: Data were analysed using SPSS software version 29.0. Fisher’s-exact test was used for categorical variables, and Mann-Whitney U test was used for continuous non-parametric variables. A p-value <0.05 was considered statistically significant. Results: Among 45 cases, 27 (60.00%) were High-TIL and 18 (40.00%) were Low-TIL. Low-TIL status showed significant association with poor differentiation, lymphovascular invasion, perineural invasion, nodal positivity, advanced pT stage, and advanced TNM stage. Positive lymph node count and exploratory composite adverse-feature score were significantly lower in the high-TIL group. Conclusion: Low stromal TIL status was associated with adverse histopathological features. However, because stromal TIL distribution was uneven across tumour sites and histological subtypes, the findings should be interpreted as exploratory pooled associations rather than site-independent conclusions.