[Synchronous multicentric osteosarcoma: with multiple primary tumors or metastatic disease. Report of one case and literature review]. / Osteosarcoma multicéntrico sincrónico con múltiples tumores primarios o enfermedad metastásica. Reporte de un caso y revisión de la literature.

Synchronous multicentric osteosarcoma, is a tumor with presentation in two or more sites without the appearance of lung metastasis. The incidence is 1 to 3% of all osteosarcomas and only less than 100 cases have been documented in the literature. In our case, we are presenting a six and a half year old patient with a painful tumor in the left thigh diagnosed with an incisional biopsy that reported a high grade conventional osteosarcoma in the left distal femur, a lesion in the contralateral limb in distal femur and proximal tibia, with no favorable response to chemotherapy. Lung and brain metastases were detected; therefore, we decided to give multidisciplinary palliative care for the disease. Years after its description there is still debate whether this condition really corresponds to a primary variable or to a manifestation of the metastatic disease.