[Large malignant mesenchymoma of the left posterior mediastinum; report of a case].

: Malignant mesenchymoma is a soft tissue tumor arising preferentially in the extremities and retroperitoneum. We report a case of primary malignant mesenchymoma of the left posterior mediastinum. A 24-year-old woman was admitted to our hospital for complaining of cough. Chest X-ray showed a giant mass occupying the 2/3 of the left hemithorax. Chest computed tomography (CT) revealed a lobulated large mass with fat density area and calcified spot in the mediastinum and left pleural space. Chest magnetic resonance imaging (MRI) demonstrated a large solid mass consisting mainly of areas with the same intensity as fatty tissue and partly of areas with heterogenous moderate intensity. The tumor was resected completely under left posterolateral thoracotomy. The pathologic diagnosis was malignant mesenchymoma; well differentiated liposarcoma with osteocartilagenous differentiation. The patient has been well for 3 years and 3 months after surgery.