PDCD1 and cutaneous melanoma: According to the current clinical data, own unpublished data by using the primary melanoma model MT/ret, which spontaneously induces multiple cutaneous melanoma and distant organ metastases, including the CNS, show that inhibition of the PD-1/PD-L1 axis resulted in diminished intracranial tumor load but failed to suppress the establishement of micrometastases in the CNS (Helfrich, unpublished data) (61, 62).