So far, there are 4 FDA approved assays of PD-L1 expression by immunohistochemistry to help guide treatment decisions for nivolumab in advanced NSCLC or melanoma, pembrolizumab in advanced NSCLC, atezolizumab in advanced UC or NSCLC, and durvalumab in advanced UC [44,58,77,90,91]. The gene discussed is CD274; the disease is melanoma.