CD274 and small cell lung carcinoma: Among all small cell carcinomas, SCLC, being the most common, has been more extensively studied and was the target of two large clinical trials that have led to revolutionary changes in the first-line treatment guidelines for ES-SCLC after decades of stagnation [6,7]. Atezolizumab [19], an immune checkpoint inhibitor that blocks the interaction of PD-L1 with PD-1 and CD80 receptors (B7-1Rs) [20].