Analytical factors such as the type of specimen used for analysing PD-L1 expression (biopsy specimen vs. excision specimen), the use of different assays to assess PD-L1, varied cut-off values, different scoring algorithms (tumour proportional scores vs. combined proportion scores) and the pattern of staining (membranous vs. cytoplasmic) for PD-L1 positivity assessment, significantly varied between studies. This evidence concerns the gene CD274 and neoplasm.