These markers have shown great promise, but there are significant limitations due to cost, assay variability and tumor heterogeneity of PD-L1 expression (McLaughlin et al. 2016; Rimm et al. 2017), need for adequate tissue, requirement for invasive biopsy, and lack of standardization for interpretation of TMB (Rizvi et al. 2015; Carbone et al. 2017; Hellmann et al. 2018). The gene discussed is CD274; the disease is neoplasm.