[Extraskeletal retroperitoneal osteosarcoma. A case report and review of the literature].

Extraskeletal osteosarcomas, localized in the retroperitoneal space, are very rare neoplasms (only 200 cases have been described); the case indicated is the second one observed in Literature. The extraskeletal osteosarcomas are very malignant mesenchymal neoplasms reproducing osseous and cartilaginous tissue disconnected from the skeletal system. From a histological point of view, the extraskeletal osteosarcomas are constituted of osseous and cartilaginous tissue with osteo-fibro-chondroblastic cells: the different representation of three types of cells define the variety of extraskeletal osteosarcomas (osteoblastic, chondroblastic, fibroblastic). Histological and ultrastructural study failed to find differences between skeletal and extraskeletal osteosarcomas. In the clinical history of some patients traumas or irradiation has been referred; although extraskeletal osteosarcomas etiology is frequently unknown. Diagnosis is generally delayed because symptoms are often absent of uncertain. Prognosis of these neoplasms is always very poor, and specially in relation to the dimension and to the possibility of its radical removal. All patients died until 2-3 years after surgery.