Prognostic Implication of Programmed Death-1-Positive Tumor-infiltrating Lymphocytes in Diffuse Large B-Cell Lymphoma

Background: Programmed death-1 (PD-1) is physiologically expressed by germinal center-associated helper T-cells and has an inhibitory effect on T-cell activity. Methods: We examined 63 cases of diffuse large B-cell lymphoma (DLBCL) and determined the number of PD-1-positive helper T-cells in a representative tumor area after immunohistochemical staining using a monoclonal antibody against PD-1. The PD-1-positive cells were counted in 3 high-power fields (HPFs; 400 x). Results: Patients were divided into 2 groups: one with a high number of PD-1-positive cells (> 20/HPF, n=33) and one with a low number of PD-1-positive cells (<= 20/HPF, n=30). The former group showed decreased overall survival, but at a statistically non-significant level (p=0.073). A high number of PD-1-positive cells was more common in patients at an advanced clinical stage and with high international prognostic index score (p=0.025 and p=0.026, respectively). The number of extranodal sites also somewhat correlated with the PD-1 staining status (p=0.071). However, the number of PD-1-positive cells was not associated with patient age, serum lactate dehydrogenase level, and Eastern Cooperative Oncology Group performance score. Conclusions: The high number of PD-1-positive cells might be associated with an unfavorable outcome in DLBCL patients.