Based on these findings, several studies showed that PD-L1 expression levels as measured by immunohistochemistry (IHC) are relatively higher in advanced NSCLC with EGFR mutation or ALK fusion compared with that of NSCLC with wild-type EGFR and ALK, though the results of some studies were inconsistent [79,80,81]. The gene discussed is ALK; the disease is non-small cell lung carcinoma.