There was a wide discrepancy between studies investigating PD-L1 expression on tumor cells, reporting a presence of PD-L1 positive tumor cells in 21.9–75% of BrM specimens (Berghoff et al., 2015, 2016a,b; Harter et al., 2015; Kluger et al., 2015; Mansfield et al., 2016; Ogiya et al., 2017; Takamori et al., 2017, 2018; Teglasi et al., 2017; Zhou et al., 2018). This evidence concerns the gene CD274 and neoplasm.