Abstract
Background
Tumor-infiltrating lymphocytes (TILs) are recognized as prognostic biomarkers. However, inconsistent TIL scores across breast cancer stages, and data are scarce for Ethiopian patients. Thus, this study evaluated TIL scores across breast cancer stages in Northwest Ethiopia.Methods
A cross-sectional study was conducted from 20 June 2024 to 19 June 2025. Using consecutive sampling, 62 breast cancer patients were enrolled, and their socio-demographic and clinicopathological data were collected using questionnaires and chart reviews. Formalin-fixed, paraffin-embedded tissue sections were stained with hematoxylin and eosin, and stromal TILs were evaluated according to the International TIL Working Group guidelines. Data were analyzed using SPSS version 27. Median TILs across clinicopathological variables were assessed using Kruskal-Wallis and Mann-Whitney U tests. Spearman correlation assessed the association of TIL scores and clinicopathological variables. P ≤ 0.05 was considered statistically significant.Results
Low TIL scores were observed in 76.5% of stage II cases, whereas high TIL scores were observed in 54.5% of stage IV cases. Median TIL percentages in stage IV (48%) and III (33%) were significantly higher than in stage II (7%), and in N2-N3 (33%) than in N0-N1 (9%) (p Conclusions
A positive correlation was found between TIL score and TNM stage. Intermediate and high TIL scores were common in advanced stages, whereas low TIL scores were prevalent in early stages. The findings suggest that advanced tumors may harbor higher mutation burdens and immunogenicity. Future research should explore the molecular subtypes of immune profiles.