[Dyspnea, fatigue and subpulmonary mass].

A 52-year-old man was referred for progressive dyspnea and fatigue. The medical history was unremarkable and there were no signs of late infections or previous tumorous diseases. Physical examination revealed diminished breath sounds and a dull tone over the right lower side. Routine blood tests, arterial blood gas and body plethysmography were all within normal ranges. Chest X-ray and thorax computed tomography (CT) showed the presence of a homogeneous subpulmonary mass with a diameter of 10 cm which had a water-like density of approximately 1 Hounsfield unit (HU). The presence of an extraordinary large pericardial cyst compromising the right lower lobe and therefore causing dyspnea was confirmed by video-assisted thoracoscopic surgery (VATS). Pericardial cysts are rare congenital mediastinal masses. They are usually asymptomatic and are usually found incidentally during routine chest X-ray, CT, magnetic resonance imaging (MRI) or echocardiography. Most pericardial cysts are situated at the right cardiophrenic angle. When reaching a relevant size they can cause symptoms such as dyspnea, coughing, chest pain and fatigue. The imaging studies most useful for diagnosis are CT, MRI and echocardiography. Differential diagnoses are diaphragmatic hernia, trapped pleural effusion or other pleural or mediastinal tumors.