In this study, the concordance in PD-L1 expression between primary BC and BM in TNBC specifically could not be studied due to small sample sizes, but authors emphasize that PD-L1 expression has previously been reported to be higher in the primary tumor compared to metastatic sites (63.7% vs. 42.2%, p < 0.0001), specifically in TNBC [52,116]. This evidence concerns the gene CD274 and breast cancer.