New-Onset Mediastinal and Central Nervous System Sarcoidosis in a Patient with Metastatic Melanoma Undergoing CTLA4 Monoclonal Antibody Treatment

SummaryBackground: Ipilimumab, a cytotoxic monoclonal antibody that inhibits cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), has been established as an effective therapy in the management of advanced melanoma. Immune-mediated adverse events are a common side effect. Case Report: A 37-year-old male patient was diagnosed with nodal and osseous metastatic melanoma 15 months after the initial surgical treatment for lower limb melanoma. Therapy with the anti-CTLA-4 antibody, ipilimumab, was started. Follow-up staging imaging after treatment initiation showed symmetrical bihilar adenopathy. Transbronchial biopsy showed sarcoidosis. The patient had associated systemic symptoms of fatigue, joint pains, anorexia and weight loss. Brain magnetic resonance imaging (MRI), which was performed for the investigation of headaches, showed abnormal enhancing tissue in the sella turcica and adjacent to the pituitary infundibulum, consistent with neurosarcoidosis. The condition was successfully treated with corticosteroids. Conclusions: We report a case of immunotherapy-induced mediastinal/hilar sarcoidosis, with pituitary involvement, mimicking tumour progression. This highlights the need for awareness amongst radiologists and oncologists of the mechanism of action and potential side effects of new immunotherapies.