We report a case of primary recurrent mediastinal dedifferentiated liposarcoma with unusual long-term survival. A woman who complained of dyspnea showed on imaging features a bulky posterior mediastinal mass which was completely excised and initially misdiagnosed as an angiomyolipoma. She recurred 15 months later and histological examination showed a dedifferentiated liposarcoma. Resection was incomplete and the patient received adjuvant therapy. Eight years later a second recurrence occurred in the right pleura and lung. The patient died three months later.