While previous studies have found a relationship between the tumor type and PD-1 or PD-L1 status, these studies have been inconsistent as to the direction of the relationship, with some studies finding a higher PD-L1 expression in squamous cell carcinoma and others noting higher PD-L1 expression in adenocarcinoma [9-10, 18-19]. This evidence concerns the gene CD274 and squamous cell carcinoma.