Representative immunohistochemical analysis of PD-L1 expression in DLBCL using a double-staining technique. (A) PD-L1⁺ DLBCL. Tumor cells were double positive for PD-L1 (brown) and PAX5 (red). Representative cases of (A) DLBCL NOS and (B) TCHRLBCL are presented. (C) mPD-L1⁺ DLBCL. Tumor cells (arrow) were positive for PAX5 and negative for PD-L1. PD-L1⁺ nonmalignant cells (arrowhead) represented 20% or more of the total tissue cellularity. (D) PD-L1^– and mPD-L1^– DLBCL. Tumor cells were positive for PAX5 and negative for PD-L1. Occasionally, PD-L1⁺ nonmalignant cells were identified; however, these represented less than 20% of the total tissue cellularity.