PDCD1 and metastatic malignant neoplasm in the lymph nodes: We then explored the relationship between cancer cell-intrinsic PD-1, PD-L1, p-S6 and co-expression of PD-L1/PD-1 proteins and clinicopathological features of NPC patients including gender, age, clinical T/N/M category, clinical stages, histological type and lymph node metastasis status.