[Pericardial effusion and mediastinal "tumor": case report of an unusual association].

A young man aged 26 was admitted as an emergency to the thoracic surgical unit for a pericardial tamponade associated with a tumour in the left anterosuperior mediastinum. After pericardial drainage by the sub-xiphoid route a left anterior mediastinotomy showed that the tumour had disappeared and a flabby diverticulum of the pericardium was found which was resected. Pericardial diverticulae are coelomic cysts which are usually considered to be congenital in origin similar to the pleuro-pericardiac cysts to which they are attached. The clinical history, which had a particularly dramatic and alarming onset is in favour of an acquired disease which is equally possible in this type of lesion.