Representative overlaid image of PD-1 and PD-L1 expression in a de novo DLBCL sample by fluorescent multiplex immunohistochemistry. Fluorescent colors show the following: blue for PD-1⁺, green for PD-L1⁺, red for CD3⁺, yellow for CD68⁺, and cyan for CD20⁺. Examples of PD-1⁺ T cells are indicated by the red arrows (co-localization of PD-1⁺ and CD3⁺ signals are shown in magenta), a PD-L1⁺ CD68⁺ cell (macrophage/dendritic cell) is indicated by the yellow arrow, and a PD-L1⁺ lymphoma cell (CD20⁺) is indicated by the white arrow. Original magnification ×20.