A female patient with stage IV-M1c (lymph node and breast metastases), chemorefractory melanoma was treated with the CTLA-4 inhibitory monoclonal antibody ipilimumab. At first evaluation following induction treatment, a marked increase in the volume and strong uptake of 18FDG in her lymphadenopathies (including new adenopathies), a marked enlargement of her spleen and interstitial lung infiltrates were observed. Non-necrotising granulomas were discovered on transbronchial biopsy and cytology on broncho-alveolar lavage established the diagnosis of sarcoidosis. There was a marked clinical and 18FDG-PET/CT documented response following 6 weeks of corticotherapy. At later follow-up, progression of melanoma metastasis in the subdiaphragmatic lymph node metastases was documented. (BELG J MED ONCOL 2012;6:58–62)