Tehran University of Medical Sciences Frontiers in Emergency Medicine 2717-3593 8 4 2024 11 11 e37 e37 Somayeh Mirbagheri Emergency Medicine Department, Tehran University of Medical Sciences, Tehran, Iran. Mohammad Afzalimoghaddam Emergency Medicine Department, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran. Maryam Edalatifard Internal Medicine Department, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran. Hadi Mirfazaelian Emergency Medicine Department, Imam Khomeini Hospital Complex, Tehran University of Medical Sciences, Tehran, Iran. 2024 11 04 2024 11 05 Pneumopericardium is a rare entity, primarily described as a result of causes such as penetrating/blunt trauma and procedures, aspergillosis, and diaphragmatic hernia. Malignancy history has also emerged as a new cause. A 67-year-old man with a history of active cancer presented to the emergency department with the chief complaint of shortness of breath and hemoptysis. He had low blood pressure and tachycardia along with hypoxia. The thoracic computed tomography (CT) imaging revealed a right pulmonary mass, central necrosis, and anterior pneumopericardium and gas adjacent to the right pericardial border.Patients with small, stable, asymptomatic pneumopericardium may be treated conservatively with close monitoring to prevent escalation to cardiac tamponade. Prompt decompression is advised if there are progressive symptoms, a concurrent pneumothorax, or cardiac tamponade. https://fem.tums.ac.ir/index.php/fem/article/view/1503 https://fem.tums.ac.ir/index.php/fem/article/download/1503/501