Abstract

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment landscape of various malignancies. However, their use is associated with a spectrum of cutaneous immune-related adverse events (cirAEs), including sarcoid-like reactions. A 64-year-old male with history of prostate cancer status post prostatectomy and metastatic renal cell carcinoma on pembrolizumab and axitinib presented with multiple papules and nodules on the extremities after eleven months of being treated with the programmed cell death protein 1 (PD-1) inhibitor. Excisional biopsy showed septal granulomatous panniculitis. Clinical examination revealed progressive bilateral hilar and mediastinal lymphadenopathy after initiation of PD-1, thought to be disease progression by patient’s oncologist. A bronchoscopy and fine needle aspiration of pulmonary lymph nodes demonstrated non-necrotizing granulomas consistent with sarcoidal granulomatous inflammation. Laboratory investigations were unremarkable, ruling out infectious etiologies. Further evaluation excluded other causes of granulomatous diseases, confirming a sarcoid-like reaction related to the PD-1 inhibitor. Sarcoid-like reactions induced by ICIs are increasingly recognized cirAEs, highlighting the complex interplay between the immune system and tumor microenvironment. Early recognition and appropriate management are crucial to minimize morbidity and improve patient outcomes.