CD274 and Merkel cell skin cancer: High expression of PD-L1 is one factor of the upregulated immune activity observed in group B. High PD-L1 expression in MCC is associated with better clinical outcomes.4 PD-L1 expression is heterogeneous, however, even in the same case.5 6 This heterogeneity complicates the usage of this immune factor as a prognostic indicator.