CD4 and head and neck squamous cell carcinoma: Patients with late stage HNSCC (UICC stage III/IV) demonstrated a slightly increased CD4/CD8 ratio compared to early stage tumors in PBMC and tumor microenvironment (3.9 ± 3.7 vs. 2.5 ±1.9; 4.4 ± 6.6 vs. 2.7 ± 3.5, respectively).