CD274 and neoplasm: Given that metastatic tumours can release EVs, mostly in the form of exosomes, that carry PD-L1 on their surface [160] and that PD-1 is upregulated in pre-metastatic sentinel lymph nodes [155], it is very likely that the immune dysfunction in the PMN might be induced by exosomal PD-L1 released by primary tumour cells.