Currently, PD-L1 expression is confirmed by immunohistochemistry (IHC), which can have low accuracy due to its sampling size: the tissue collected represents only a small site that may not accurately represent the intra and inter-heterogeneity of PD-L1 expression across multiple tumor sites or how it temporally changes during other therapies [9,10,11,12]. The gene discussed is CD274; the disease is neoplasm.