Examples of PD-L1 staining patterns observed and categorized in this NSCLC series.

<p><b>A</b>: Pattern I—Constitutive mixed with induced. Diffuse expression of PD-L1 (IHC) on tumor cell membranes of a squamous cell carcinoma, including central regions of trabeculae. Prominent labeling of cells in the TME compartment at the tumor-nest-TME interface suggesting presence of an immunological synapse (inset arrow). <b>B</b>: Pattern II—Induced only. Patchy expression of PD-L1 in a squamous cell carcinoma at the tumor-nest-TME interface (inset arrow). Minimal to no PD-L1 expression in the trabeculae (asterisk) if compared with (<b>A</b>). <b>C</b>: Pattern III—Immune ignorance. No to minimal PD-L1 expression in both tumor and TME compartments in an adenocarcinoma. <b>D</b>: Pattern IV—Constitutive only. Diffuse expression of PD-L1 by tumor-nests in an adenocarcinoma with minimal TME staining. <b>E</b>: Pattern V—TME expression only. No to minimal PD-L1 expression in tumor cells of a squamous cell carcinoma, with widespread staining in the TME compartment. <b>F</b>: Percentages of PD-L1-positive tumor cells in all staining pattern categories (I-V). <b>G</b>: Percentages of TME PD-L1-positive cells in all staining pattern categories (I-V). <b>H</b>: Digital H-scores from tumor-nests in all staining pattern categories (I-V). Significant differences between groups I and II were calculated using two-tailed Student’s t-tests, assuming unequal sample variances (*<i>P</i> ≤ 0.05, **<i>P</i> ≤ 0.01, ***<i>P</i> ≤ 0.001 and ****<i>P</i> ≤ 0.0001). Scale bars: 200 μm (<b>A-E</b>). NSCLC = non-small cell lung carcinoma; IHC = immunohistochemistry; TME = tumor microenvironment.