Finally, a study harnessing the power of a new method for single-cell cytometry investigations, FAUST, uncovered a population of effector memory CD4+ and CD8+ T-cells co-expressing CD28, HLA-DR, and PD-1 in the peripheral blood of MCC patients, which may be a candidate biomarker for response to pembrolizumab. The gene discussed is CD8A; the disease is Merkel cell skin cancer.