Sarcoid-like reaction in malignant melanoma exacerbated with pembrolizumab therapy case report

Sarcoid Like Reaction (SLR) is a localized non-caseating epithelioid granulomatous reaction seen secondary to certain immunotherapies and malignancies. Invasive melanoma, while being associated with onset of sarcoidosis, has not shown to directly induce SLR in the literature. We present the case of a 68-year-old male with malignant melanoma, who was found to have SLR prior to starting immunotherapy, which worsened while on pembrolizumab. This case highlights the challenge of distinguishing between drug-induced SLR and melanoma-induced SLR, and the implications in terms of management.