CD274 and Merkel cell skin cancer: As MCC cells often express programmed cell death protein ligand 1 (PD-L1) and Merkel cell polyomavirus (MCPyV)-specific T cells express corresponding PD-1, blockage of the PD-1 immune inhibitor pathway is of interest and PD-1/PD-L1 inhibitors have been shown to be a promising approach for the treatment of advanced MCC [5, 6].