[A Well-differentiated Mediastinal Liposarcoma that Expanded into the Right Thoracic Cavity with Dedifferentiation].

A 77-year-old man was referred to our hospital because of massive opacification of the right hemithorax on chest radiography. Chest computed tomography (CT) revealed a 25×18-cm heterogeneous tumor in the right hemi-thorax. Chest CT scan obtained 6 years before the referral showed an 8×2-cm homogeneous lipomatous mass in the anterior mediastinum suggesting a well-differentiated liposarcoma. The follow-up chest CT scan obtained 12 months before the referral showed a 4×2-cm heterogeneous solid component within the lipomatous mass of the mediastinum suggesting the development of a dedifferentiated liposarcoma. The tumor was completely resected through a median sternotomy and anterior right thoracotomy. The pathological diagnosis was dedifferentiated liposarcoma originating from a well-differentiated liposarcoma of the anterior mediastinum.