Indeed, we show that 73% of MBCs have tumoural expression of PD-L1, marking them as a suitable cohort for immunotherapy targeting the PD-1/PD-L1 checkpoint, especially in light of the impressive response to pembrolizumab as documented by Adams et al.21 We do not see any associations between PD-L1 or TILs, nor with BCSS in this MBC cohort. Here, CD274 is linked to maternal uniparental disomy of chromosome 20.