Giant pericardial cyst presenting as pneumonia.

A 71-year-old woman presented with symptoms of dyspnea, cough, and fever. Chest radiography revealed interstitial infiltrates, which confirmed the diagnosis of pneumonia. In addition, a low-density mass adjacent to the right side of the heart was identified (Fig. 1). Chest computed tomography and transthoracic echocardiography indicated the presence of a mass of water-density opacity that was compressing the right atrium (Fig. 2). Cardiovascular magnetic resonance suggested a pericardial cyst, which usually presents as a homogeneous mass located in the right anterior cardiophrenic angle, with high signal intensity on T2-weighted images and low-to-intermediate signal intensity on T1-weighted images. Furthermore, there was no gadolinium enhancement, which confirmed the avascular and likely benign nature of the mass1 (Fig. 3). Because of the large size of the mass and its effect on the heart, the patient underwent video-assisted thoracoscopic excision of the mass, which was located in the right cardiophrenic angle, adjacent to the right atrium (Fig. 4A). Histologic examination confirmed that the mass was a pericardial cyst (Fig. 4B). Fig. 1 Chest radiography. A) Posteroanterior and B) lateral views show a mass (arrow) in the right cardiophrenic angle. Patches of infiltrates are seen in both lung fields. Fig. 2 A) Chest computed tomography (cross-section) and B) transthoracic echocardiography (apical 4-chamber view) show a large, unilocular, thin-walled structure (arrow) of water-density opacity, located lateral to the right atrium and compressing both ... Fig. 3 Cardiovascular magnetic resonance shows a large, well-defined extracardiac mass (arrow) in the right cardiophrenic space, with partial compression of the right atrium and bowing of the interatrial septum to the left. A) A T1-weighted image and ... Fig. 4 Pathology specimen. A) Macroscopic view shows an oval-round cystic lesion (8 cm at largest diameter) filled with clear, watery fluid. B) Microscopic view shows that the cystic wall is composed of hypocellular fibroconnective tissue (arrows) with ...