[Cardiac tamponade due to a pleuropericardial cyst with invasive lung cancer].

Pericardial and pleuropericardial cysts are uncommon (7% of all mediastinal masses) and in the majority of cases are symptomatic and it is usually a casual finding. We present the case of a 62 year-old male with a left-sided pleuropericardial cyst which had the development of a cardiac tamponade; a rare finding in this type of disease. After it was surgically removed, the histopathology showed infiltration of the cyst by a poorly differentiated large cell carcinoma.