PDCD1LG2 and melanoma: In melanoma patients treated with ipilimumab and nivolumab, the expression of PD-L1 on immune-infiltrating cells had an even stronger predictive value, than the expression of PD-L1 on tumor cells (13), warranting further research into the role of PD-L1 and PD-L2 on stromal compartment cells versus tumor cells.