18F-FDG PET/CT of Multiorgan Sarcoid-Like Reaction During Anti-PD-1 Treatment for Melanoma.

We report a case of a 50-year-old woman treated with anti-PD-1 inhibition for metastatic melanoma. During treatment, extensive and transient histopathologically confirmed sarcoid-like reaction was detected in multiple organ systems and at different time points using F-FDG PET/CT imaging. Immune-related adverse events during anti-PD-1/PD-L1 antibody treatment are increasingly being reported. This case report emphasizes the broad spectrum of possible presentations of sarcoid-like reaction detected by F-FDG PET/CT and its evolution in time. For the clinician, awareness of these immune-related adverse events helps to accurately interpret findings on imaging.