Expression of PD-1 on CD4+ Tumor-Infiltrating Lymphocytes in Tumor Microenvironment Associated with Pathological Characteristics of Breast Cancer

Objective. This study aimed to investigate the correlation of CD4+/PD-1+ or CD4+/PD-1− tumor-infiltrating lymphocytes with pathological characteristics in breast cancer patients. Methods. A cross-sectional study consecutively recruited 133 patients with invasive ductal breast cancer. The expression of CD4, programmed cell death protein 1 (PD-1), CK7, CK20, E-cadherin, or Ki-67 was detected by immunohistochemistry. The associations between CD4+/PD-1+ or CD4+/PD-1− tumor-infiltrating lymphocytes and pathological characteristics were evaluated. Results. Elderly patients intended to have a lower level of CD4+/PD-1− tumor-infiltrating lymphocytes (p<0.05). Patients with positive E-cadherin expression had higher median cell counts of CD4+/PD-1− tumor-infiltrating lymphocytes than patients with negative E-cadherin expression (30/HPF versus 10/HPF, p<0.05). Counts of CD4+/PD-1+ tumor-infiltrating lymphocytes had a significant correlation with Ki-67 index that the correlation coefficient was 0.29 (p=0.001). Positive CK20 expression was related to a higher level of CD4+/PD-1− tumor-infiltrating lymphocytes than negative CK20 expression (73/HPF versus 30/HPF, p