Immunohistochemical stains in the study. High (A) and low (B) proportion of PD-1⁺ (brown) leukocytes. High (C) and low (D) proportion of PD-L1⁺ (brown) leukocytes. High (E) and low (F) proportion of PD-L2⁺ (brown) leukocytes. Red, PAX5. Original magnification ×400 for all panels.