PDPN and melanoma: This inverse correlation was validated in both primary (r = −0.2884, p < 0.05; Figure 2H) and metastatic (r = −0.444, p < 0.01; Figure 2I) melanomas, substantiating PDPN’s dual immunosuppressive role in immune checkpoint activation and impairment of T cell infiltration, in agreement with transcriptomic deconvolution data.