Most common nonhematologic primary malignant neoplasm of bone in children and adolescents.
Pain and swelling are the most common presenting symptoms.
Although it can occur at any age, it usually affects patients in the second and third decade of life with a peak incidence between 13 and 16 years of age. It is more common in males than females.
Chemotherapy combined with surgery is the standard of care.
Prognosis of patients with localized disease has improved substantially following the introduction of chemotherapy, with 75% to 80% 5-year survival rates.
The WHO defines osteosarcoma as a primary osseous malignant neoplasm composed of mesenchymal cells producing osteoid and immature bone, even if only in small amounts. 
Director of the Musculoskeletal Tumor Program
Associate Professor of Oncology
Bloomberg Children's Center
The Johns Hopkins Hospital
DL declares that he has no competing interests.
Dr David Loeb would like to gratefully acknowledge Dr Luminita Rezeanu and Dr Michael J. Klein, the previous contributors to this monograph. LR and MJK declare that they have no competing interests.
Professor of Surgery
Ellis Fischel Cancer Center
University of Missouri
ES declares that he has no competing interests.
Locum Consultant Paediatric Oncologist
University College Hospital
RW declares that she has no competing interests.
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