The expression of PD-L1 on tumor cells has been associated with good prognosis and sustained clinical responses in immunotherapeutic regimens based on PD-L1/PD-1/CTLA4 immune checkpoint blockade; however, the relative importance of PD-L1 expression on tumor cells versus immune cells in the tumor microenvironment is a matter of controversy. This evidence concerns the gene CTLA4 and neoplasm.