CTICasesPembrolizumab-Induced Sarcoid-Like Reaction
Imaging findings
Follow-up chest CT scans in an oncology patient treated with pembrolizumab demonstrate new-onset symmetric hilar and mediastinal lymphadenopathy and bilateral perilymphatic small pulmonary nodules, primarily in an upper-lobe distribution, mimicking classic sarcoidosis. Transbronchial biopsy demonstrates well-formed, compact, non-necrotizing granulomas. Follow-up imaging after discontinuation of the drug shows complete resolution of both parenchymal nodules and lymphadenopathy.
Key takeaways
Immune checkpoint inhibitors can trigger immune-related adverse events, including sarcoid-like granulomatous reactions that mimic sarcoidosis both radiographically (symmetric adenopathy, perilymphatic nodules) and histologically (non-caseating granulomas). Recognizing this reaction is critical to avoid misinterpreting the findings as tumor progression, and the condition generally resolves following drug cessation or corticosteroid therapy.
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