[69 year-old patient with opaque hemithorax on the right side].

Liposarcomas are the most common sarcomas in adults. Mediastinal occurrence is very rare. We report on a 69 year-old man with a huge tumor in the right pleural cavity leading to a complete atelectasis of the right lung. The tumor could be completely resected. Histology showed a well-differentiated liposarcoma of the mediastinum. One year after resection there was no evidence for local recurrence or metastatic spread.