PDCD1 and ulnar-mammary syndrome: While Programmed cell Death protein-1 (PD1), Programmed Death Ligand-1 (PD-L1), and Cytotoxic T-Lymphocyte-Associated protein-4 (CTLA-4) blockade showed successful responses in patients with cutaneous melanoma (7, 8), patients with UMs were excluded from these studies because their molecular characteristics tend to be widely different from cutaneous melanoma (9, 10).