DEDIFFERENTIATED CHONDROSARCOMA OF THE RIB WITH A MALIGNANT MESENCHYMOMATOUS COMPONENT - AN AUTOPSY CASE-REPORT

A rare variant of dedifferentiated chondrosarcoma with malignant mesen chymomatous component in a 57-year-old male is reported. The patient p resented with a posterior mediastinal mass arising from the left eight h and ninth ribs showing well differentiated, low-grade chondrosarcoma . Five years later, local recurrence occurred and an excised specimen also showed the same histological features as the primary tumor. Anoth er 6 years later, the tumor recurred and metastasized to the multiple organs, the patient dying 4 months later. Autopsy revealed that the re current and metastatic tumors showed malignant mesenchymomatous 'dedif ferentiation' of chondrosarcoma composed of rhabdomyosarcoma, angiosar coma, chondrosarcoma, osteosarcoma, and leiomyosarcoma, in addition to fibrosarcomatous areas. Although the less differentiated component of dedifferentiated chondrosarcoma usually shows the histological featur es of malignant fibrous histiocytoma and fibrosarcoma, multilineage di fferentiation can occur in that component. The phenomenon of 'dediffer entiation' in chondrosarcoma and the relationship to and distinction f rom malignant mesenchymoma of soft tissue and bone are discussed.