CD274 and squamous cell carcinoma: In primary tumors, higher PD-L1 positivity was observed in squamous cell carcinoma (SCC) and wild-type EGFR than in adenocarcinoma and mutant EGFR, respectively (adenocarcinoma, 13.5% vs. 5.4%, P = 0.005; mutant EGFR, 18.9% vs. 0% P = 0.05; Table 2).