Tumour-infiltrating lymphocytes are associated with sentinel lymph node metastasis in early breast cancer: a cross-sectional study

Tumour-infiltrating lymphocytes (TILs) reflect the host immune response within the tumour microenvironment and have been associated with clinicopathological outcomes in breast cancer. This study evaluated the association between stromal TIL levels and sentinel lymph node metastasis (SLNM) in patients with clinically node-negative early breast cancer. This single-centre cross-sectional study included women with cT1–2N0M0 breast cancer who underwent sentinel lymph node biopsy between 1 January 2018 and 31 December 2025. Clinicopathological data were obtained from institutional records. Stromal TILs were assessed by a single pathologist according to the recommendations of the International TILs Working Group 2014. Associations between clinicopathological variables and SLNM were initially assessed using appropriate univariable analyses. Variables with a p value < 0.25 in univariable logistic regression were entered into a multivariable logistic regression model. Odds ratios (ORs) with 95% confidence intervals (CIs) were reported. Among 241 patients, 67 (27.8%) had SLNM. Low, intermediate, and high TIL levels were observed in 159 (66.0%), 42 (17.4%), and 40 (16.6%) patients, respectively. TIL category was significantly associated with SLNM ( p = 0.023), with the highest proportion of SLNM observed in the low-TIL group. In multivariable logistic regression, higher TIL levels were associated with lower odds of SLNM (adjusted OR 0.977, 95% CI 0.961–0.994; p = 0.007). Lymphovascular invasion was also independently associated with SLNM (adjusted OR 0.290, 95% CI 0.156–0.537; p < 0.001). Tumour size was associated with SLNM in univariable analysis but not after multivariable adjustment. Higher stromal TIL levels and the absence of lymphovascular invasion were associated with lower odds of sentinel lymph node metastasis in this cohort of patients with early breast cancer. Further prospective studies with external validation are required to determine whether TIL assessment can contribute to clinically useful prediction of nodal status.