[Recommendations from the group of bone tumors of the French Childhood Cancer Society and the French Sarcoma Group/Group for the Study of Bone Tumors].

Osteosarcomas of the mandible represent 3-8% of osteosarcomas. The rarity of this anatomic site and its specific treatment explain that only retrospective and a few prospective studies are available in literature. However, there is a consistent evidence on the natural history and treatment of these tumors, which clearly differentiates them from osteosarcomas of the long bones. The aim of this study was to draw up recommendations based on these data and on a retrospective study by the French Sarcoma Group (GSF-GETO). Osteosarcomas of the mandible should be centrally reviewed by an expert pathologist. MDM2, GNAS and RASAL1 status should be checked, and a fragment should be frozen. Complete surgical resection with wide margins is the cornerstone of treatment. Mandibular reconstruction techniques can reduce the sequelae. Contrary to the validated treatment for osteosarcomas of limbs, the role of chemotherapy to prevent metastasis or local recurrence has yet to be clarified for mandibular osteosarcomas. The role of postoperative radiotherapy, in adults, should be discussed for these tumors, whose wide soft-tissue resection may be difficult to confirm. In children, adjuvant chemotherapy is preferable in cases of uncertain/possibly incomplete resection. Relapse of mandibular osteosarcomas is primarily local. Pulmonary metastases are delayed and less frequent than in long-bone osteosarcomas. The overall survival rate at five years is about 70%.