What Ultrasounds, Sometimes, Cannot See: A Case of Posterior Pericardial Cyst

Pericardial cysts (PCs) are very rare, often congenital, mediastinal masses. Usually, they are located in the right cardiophrenic angle and only in 8% of cases in the anterior or posterior mediastinum. Computed tomography and/or magnetic resonance imaging are accurate tools for the diagnosis and characterization of mediastinal masses. However, echocardiography is, in many cases, a good screening technique. If asymptomatic, they do not require surgical excision. The authors describe a case of posterior mediastinum PC; in these cases, echocardiography cannot see the mass and three-dimensional imaging techniques are required. The clinical management of this case is discussed.