Abstract

Extraskeletal osteosarcoma is a rare malignant tumor of soft tissue. In addition, there are only several cases of osteosarcoma of the mediastinum as a primary site in the world. We report a case of extraskeletal osteosarcoma arising in the posterior mediastinum. A 54-year-old man visited our hospital because of chest pain. Chest CT showed a 12 cm sized huge mediastinal mass. The mass revealed solid and ivory-colored cut surface with multifocally ovoid cystic spaces and hemorrhage. Microscopically, the tumor consisted of polygonal stromal cells, giant cells and varying amounts of neoplastic new bone, and mitotic figures were frequently observed. There were no distant metastasis and regional lymph node involvement.

• Keywords: Extraskeletal Osteosarcoma-Mediastinum;