Quantification of Regulatory T Cells Enables the Identification of High-Risk Breast Cancer Patients and Those at Risk of Late Relapse

PURPOSE: To assess the clinical significance of tumor-infiltrating FOXP3-positive regulatory T cells (TR) in breast cancer patients with long-term follow-up. PATIENTS AND METHODS: FOXP3-positive TR were detected by immunohistochemistry with our new, extensively characterized FOXP3 monoclonal antibody, 236A/E7. Numbers of FOXP3-positive lymphocytes in tissue microarray cores from pure ductal carcinoma in situ (DCIS; n = 62), invasive breast cancer (n = 237) or from comparable areas of normal terminal duct lobular breast tissue (n = 10) were determined. A median cutoff of > or = 15 defined patients with high numbers of TR. RESULTS: TR numbers were significantly higher in in situ and invasive breast carcinomas…