In a study of 41 patients with metastatic melanoma treated by anti-CTLA-4 (ipilimumab), four patients among the 31 having disease control had a sarcoid-like mediastino-hilar lymphadenopathy diagnosed on the follow-up 18FDG PET/CT, while this side effect was not observed on the 10 patients having progressive disease [86]. This evidence concerns the gene CTLA4 and metastatic melanoma.