Giant liposarcoma is an unusual variant of mediastinal tumors. The case of a 73-year-old woman is reported. She presented with a posterior mediastinal tumor invading the third middle tract of the thoracic esophagus and the adventitia of the descending aorta, close to the posterior pericardium; a neoplastic thrombus 2cm in size was located in the upper left pulmonary vein. The tumor was completely excised by left thoracotomy, in extracorporeal circulation. The postoperative course was uneventful and the patient received adjuvant chemotherapy. She is currently alive after 8 months, disease-free. The natural history, pathology, and prognosis of the disease are reviewed and management of such lesions is discussed.