The authors report the case of a 62 year old patient admitted for a tamponade, revealing a mixed lympho-epithelial thymoma with invasion of the pericardium, the aorta and of the pulmonary arteria. The histological diagnosis was confirmed by a surgical biopsy performed after emergency pericardiocentesis. A neoadjuvant chemotherapy was administered followed by incomplete surgical resection and then a post operative radiotherapy. A local relapse was diagnosed at one year follow up by CT scan and a second line chemotherapy was administered. No further relapse occurred and patient was alive at four years.