CD274 and mucosal melanoma: Using the same threshold as described for MET, 12% (2 of 17) of nevi, 70% (30 of 42) of primary cutaneous melanoma, 80% (16 of 20) of primary mucosal melanoma, and 50% (11 of 21) of metastatic melanomas demonstrated PD-L1 expression by more than 20% of cells.