CD274 and neoplasm: However, there are a number of PD-L1 testing limitations that can confound its use as a predictive biomarker, including the heterogeneity and dynamics of PD-L1 expression, the varying performance of the various immunohistochemistry-based assays with different cutoffs, the absence of consensus regarding the relevance of geographic patterns of expression of PD-L1 or its expression on tumor or inflammatory cells within the tumor microenvironment and, finally, the availability of an adequate sample [15].