In MCC, overexpression of Chemokine (C-C motif) ligand 1 (CCL17/TARC) and C-C chemokine receptor type 4 (CCR4) leads to the attraction of many CD4+ regulatory T cells, Th2 and Th17 cells (Rasheed et al., 2018). This evidence concerns the gene CCL17 and Merkel cell skin cancer.