Primary cardiac tumors are rare events. We describe here a case of undifferentiated pleomorphic sarcoma (so-called pleomorphic malignant fibrous histiocytoma) obliterating mostly the left side and the anterior wall of pericardium in a 84-year-old man admitted for mild dyspnea at rest. The diagnosis was suspected after excluding the lung origin of the mass (observed by plain chest radiography) by thorax computed tomography but it was confirmed only by cardiac-gated magnetic resonance imaging and transthoracic biopsy. Considering both patient's age and comorbidity, and local extension of the lesion, after counseling with cardiac surgeons and oncologists, the patient was treated only by conservative medical therapy. The patient died 6 months after the diagnosis due to a superior vena cava syndrome as an effect of infiltration and obstruction of superior vena cava by the tumor at the site of vein entry in the right atrium. This case is an example of a primary cardiac tumor that causes relative myocardial sufferance both by infiltration and by limitation of normal heart diastolic function
