In summary, the PD-L1 biomarker discussed here highlights the importance of understanding the practice of IHC. This can be used to the patients advantage, with appropriate usage. The currently available literature on PD-L1 IHC from a methodologic point of view has not shown that different assays are comparable. The route of laboratory developed test and commercial test validation is the same: challenging and complex. Executing this process along proper methodologic lines is needed to ensure that patients receive the most accurate and representative test outcomes.