Immune-related Pulmonary Granulomas Mimicking Metastatic Lesions in a Lung Cancer Patient

Immune checkpoint inhibitors are widely used in non–small cell lung cancer but can cause immune-related adverse events. FDG-avid pulmonary granulomas are unusual and may be mistaken for metastases. We report a 72-year-old man with mucinous adenocarcinoma treated with immunotherapy who developed new FDG-avid, well-circumscribed, round lung nodules, initially suspected as metastases. Biopsy revealed non-necrotizing granulomas, and the nodules regressed without corticosteroids. This case highlights a diagnostic pitfall during immunotherapy, where immune-related granulomas can resemble disease progression. Clinician awareness is essential to avoid unnecessary interventions and ensure appropriate management.