Pericardial Cyst

History: Male with chest pain. 

Pericardial Cyst – Coronal CT of the Chest with intravenous contrast reveals a simple unilocular low attenuation collection at the right cardiophrenic angle (yellow arrow).

This is the classic location and appearance of a pericardial cyst, which is an outpouching of the parietal pericardium that collects simple fluid. Pericardial cysts represent 6% of mediastinal masses.

See the differential diagnosis of caridophrenic angle masses here.