CD274 and breast cancer: We, therefore, applied multi-level testing of PD-L1 expression in two early BC patient cohorts (both treated and untreated), including: (a) immunohistochemical (IHC) staining with two different commercially available antibody clones; (b) RNA fluorescent in situ hybridization (RNA-FISH) combined with immunofluorescence (IF) for simultaneous detection of mRNA-protein expression on the same tissue section; (c) bulk PD-L1 gene expression; and (d) multiplex fluorescent immunohistochemistry.