McIntosh, Lacey JRuppell, Evan CBarile, Maria2023-05-022023-05-022023-03-24McIntosh LJ, Ruppell EC, Barile M. Atypical and Typical Distant Sarcoid-like Reactions during Treatment of Metastatic Melanoma. Radiol Imaging Cancer. 2023 Mar;5(2):e220177. doi: 10.1148/rycan.220177. PMID: 36961316; PMCID: PMC10077081.2638-616X10.1148/rycan.22017736961316https://hdl.handle.net/20.500.14038/52018Images in cancer: Sarcoid-like reactions are reported in 4%–14% of patients with cancer and are likely driven by T-cell–mediated hypersensitivity reactions forming granulomas (1). They can occur with infection, treatment, or the presence of foreign bodies (2) and have been increasingly reported in the era of precision targeted and immune checkpoint inhibitor therapy (3,4), including the use of BRAF and MEK inhibitors (Figure) (5). The classic pattern mimics sarcoidosis and involves mediastinal and hilar lymph nodes, which may be enlarged and demonstrate increased fluorodeoxyglucose (FDG) uptake at FDG PET/CT; pulmonary nodules and infiltrates may or may not be present (1,2). The incidence of extrathoracic sarcoid-like reactions is unknown but rare (6), with case reports documenting reactions including the liver, spleen, skin, central nervous system, pancreas, bone, and eyes (6,7). Absence of findings at baseline and emergence after treatment initiation can be helpful to identify a sarcoid-like reaction, although it may be indistinguishable from disease and may require tissue sampling. Radiologists should recognize these patterns to avoid confusion with disease progression. If necessary, steroids are the mainstay of treatment; immunotherapy discontinuation may be required in severe cases.enMolecular Imaging–CancerPET/CTJournal ArticleRadiology. Imaging cancer