The impact of tumor-infiltrating lymphocytes on tumor features and pathological characteristics in breast cancer patients: the role of cytotoxic T lymphocytes and regulatory T cells

OBJECTIVE: Though tumor-infiltrating lymphocytes (TILs) have a predictive impact in cancer patients. their association with presentation and prognosis in breast cancer is less consistent. This study aimed to assess the level of infiltrating cytotoxic T lymphocytes (CTLs) and regulatory T lymphocytes (Tregs) and their association with the clinicopathological features of breast cancer. PATIENTS AND METHODS: Tissue samples from female patients (n=153) diagnosed with primary invasive breast cancer were stained with CD8 (a CTL marker) and Foxp3 (a Treg marker) using immunohistochemistry. RESULTS: CTLs were distributed between tumor bed and stroma whereas Treg cells were mainly located in the stroma. The level of intratumoral CTLs correlated positively with Tregs in both tumor and stroma (rho=0.312. p<0.001 and rho=0.176, p=0.031: respectively). Stromal CTLs correlated positively with stromal Tregs (rho=0.319. p=0.005). Tumor size correlated inversely with the number of Treg cells in the tumor bed (rho= - 0.179. p=0.028). Tregs were associated with lymphovascular invasion status in the tumor bed (p=0.042). The ratio of intratumoral CTLs to Tregs was associated with estrogen receptor positivity and luminal subtype (p=0.029 and p=0.045, respectively). The median number of CTLs was significantly lower in patients using aspirin or antihypertensive medications compared to nonusers (p=0.024 and p=0.03. respectively). CONCLUSIONS: TILs were distributed differently in tumor tissues of breast cancer patients. CTLs infiltrates were found in both tumor bed and stroma while Tregs were dominant in the stroma. TILs were also distinctly associated with tumor features. The impact of TILs on prognosis and treatment outcomes in Jordanian breast cancer patients needs further investigation.