Primary Dedifferentiated Liposarcoma of the Posterior Mediastinum With a Positive Surgical Margin.

Liposarcoma often occurs in the extremities and retroperitoneum. Primary mediastinal liposarcoma is uncommon, and there is no settled opinion regarding adjuvant therapy after surgery. We have recently experienced a relatively rare case of primary dedifferentiated liposarcoma of the posterior mediastinum. The patient was a 76-year-old woman. An abnormal shadow was noted in the posterior mediastinum. Esophageal submucosal tumor and gastrointestinal stromal tumor were suspected; endoscopic ultrasound-guided fine needle aspiration was performed, but a definitive diagnosis could not be obtained. As the tumor tended to slowly grow, surgical resection was performed. Based on histopathological findings, the patient was diagnosed with primary dedifferentiated liposarcoma of the posterior mediastinum. Owing to the presence of a positive surgical margin, postoperative radiotherapy (60 Gy/24 fr/6 w) was administered. No recurrence was observed after three and a half years of follow-up. The prognosis of primary dedifferentiated liposarcoma of the posterior mediastinum with a positive surgical margin is poor, but postoperative radiotherapy may be useful.