PD-L1 expression detected by immunohistochemistry has become an FDA-approved companion diagnostic test for pembrolizumab treatment in non-small cell lung carcinoma (NSCLC), gastric/gastroesophageal junction adenocarcinoma, cervical cancer, and urothelial cancer [45], [46], [47], [48]. The gene discussed is CD274; the disease is non-small cell lung carcinoma.