Because PD-L1 expression in tumour tissues is inducible via various mechanisms at the genetic, epigenetic, transcriptional, post-transcriptional, and post-translational levels [45–47], the timing of biopsy for PD-L1 IHC is important for assessing PD-L1 expression as a biomarker of response to ICI therapies. This evidence concerns the gene CD274 and neoplasm.