Fig. 3
Immunohistochemistry highlights the lack of tumor cell PD-L1 staining and the presence of immune cell PD-L1 staining in a colonic adenocarcinoma. H&E shows that the tumor has a solid growth pattern (A). Single antibody PD-L1 stain shows positively stained cells both at the tumor-stroma interface and within the tumor cell nest; some positively stained cells, especially those within the tumor cell nest (such as the arrow indicated ones), show nuclear features difficult to distinguish from that of the tumor cells (B). By double-antibody immunohistochemistry (PD-L1 + SATB2), it becomes clear that the PD-L1 positive cells (red chromogen, red-arrow indicating two example cells) are all negative for SATB2; in contrast, all cells that are positive for SATB2 (i.e., tumor cells) are negative for PD-L1 (C)
