The prognostic significance of FOXP3 expression in patients with metastatic HER2-positive breast cancer

Background. The effectiveness of targeted therapy in patients with HER2+ breast cancer largely depends on the tumor microenvironment. Regulatory T-lymphocytes (FOXP3+) negatively regulate immune responses and are mostly considered a factor of unfavorable prognosis. Breast cancer is a heterogeneous disease with unique biological properties for each molecular subtype. The impact of regulatory T cells on the prognosis of HER2+ breast cancer is controversial.