Figure 1.

Immunohistochemical. expression of programmed death‐1 (PD‐1) and PD‐ligand 1 (PD‐L1) in low‐grade and high‐grade clear cell renal cell carcinoma (ccRCC) tissues without pretreatment. Paraffin sections were reacted with anti‐PD‐1 (A‐F) or PD‐L1 (G‐L). In low‐grade ccRCC, a small number of tumor‐infiltrating immune cells (TIIC) were positive for PD‐1 (A‐C), whereas many PD‐1‐positive TIIC were found in high‐grade tumors (D‐F). No PD‐L1 expression was found in low‐grade ccRCC tissues (G‐I), and PD‐L1 expression was mainly observed in TIIC in high‐grade tumors (J‐L). Some tumor cells sporadically showed membranous PD‐L1 staining (K). Scale line = 50 μm. Blue curve (A,D,G,J) outlines the areas of the tumor nest and periphery. Arrows in B, C, E, F indicate PD‐1‐positive TIIC, arrows in K, L indicate PD‐L1‐positive TIIC and arrowheads in K indicate PD‐L1‐positive tumor cells