CTLA4 and cutaneous mastocytosis: Survival in metastasized cutaneous melanoma (CM) has been greatly improved with the advent of kinase inhibitors for BRAF‐mutant tumors and monoclonal antibodies against the cytotoxic T‐lymphocyte‐associated protein 4 (CTLA4) and Programmed cell death protein 1 (PD‐1) immune checkpoints.2 Used as single agents, response rates of 10%‐20% for anti CTLA4 and 40% for anti‐PD‐1 have been reported.