Osteosarcoma is the most common form of malignant bone tumor; it is characterized by malignant mesenchymal cells producing osteoid or immature bone. The tumor predominantly involves children, teenagers and young adults with a peak of incidence in the second decade of life during the adolescent growth spurt, suggesting a correlation with rapid bone proliferation. Osteosarcoma originates more frequently in the methaphyseal region of long bones, with particular involvement of the distal femur (40%), proximal tibia (25%) and humerus (15%); 80% of osteosarcomas occur in the limbs, whereas 20% affect the axial skeletal and pelvis. Osteosarcoma arises from the medullary cavity and grows toward the cortex and adjacent soft tissue. The osteosarcoma leads to death within a matter of months if left untreated. In the 1970s, the use of adjuvant chemotherapy in the treatment increased survival in patients with osteosarcoma. Pathological fractures and local diffusion of tumors are associated to a poor prognosis.