Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can then spread to other areas of the body. To learn more about cancer and how it starts and spreads, see What Is Cancer?
Osteosarcoma (also called osteogenic sarcoma) is the most common type of cancer that starts in the bones. The cancer cells in these tumors look like early forms of bone cells that normally help make new bone tissue, but the bone tissue in an osteosarcoma is not as strong as that in normal bones.
Most osteosarcomas occur in children, teens, and young adults. Teens are the most commonly affected age group, but osteosarcoma can develop at any age. (For information about the differences between childhood cancers and adult cancers, see Cancer in Children.)
In children, teens, and young adults, osteosarcoma usually starts in areas where the bone is growing quickly, such as near the ends of the leg or arm bones:
Still, osteosarcoma can develop in any bone, including the bones of the pelvis (hips), shoulder, and jaw. This is especially true in older adults.
Based on how the cancer cells look under the microscope, osteosarcomas can be classified as high grade, intermediate grade, or low grade. The grade of the tumor tells doctors how likely it is that the cancer will grow quickly and spread to other parts of the body.
These are the fastest growing types of osteosarcoma. When seen with a microscope, they do not look like normal bone, and many of the cancer cells are in the process of dividing into new cells. Most osteosarcomas that occur in children and teens are high grade. There are many types of high-grade osteosarcomas (although the first 3 are the most common).
Other high-grade osteosarcomas include:
These uncommon tumors fall between high-grade and low-grade osteosarcomas. (They are usually treated the same way as low-grade osteosarcomas.)
These are the slowest-growing osteosarcomas. The tumors look more like normal bone and have few dividing cells when seen with a microscope.
The grade of the tumor plays a role in determining its stage and the type of treatment used. For more on staging, see Osteosarcoma Stages.
Several other types of tumors can start in the bones.
Ewing tumors (Ewing sarcomas) are the second most common bone cancer in children. They are described in Ewing Family of Tumors.
Most other types of bone cancers are usually found in adults and are uncommon in children. These include:
For more information on these cancers, see Bone Cancer in Adults.
Many types of cancer that start in other organs of the body, especially cancers in adults, can spread to the bones. These are sometimes referred to as metastatic bone cancers, but they are not true bone cancers. For example, prostate cancer that spreads to the bones is still prostate cancer and is treated like prostate cancer. For more information, see Bone Metastasis.
Not all bone tumors are cancer. Benign bone tumors do not spread to other parts of the body. They are usually not life threatening, and surgery can often remove them completely. There are many types of benign bone tumors, including:
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Gorlick R, Janeway K, Marina N. Chapter 34: Osteosarcoma. In: Pizzo PA, Poplack DG, eds. Principles and Practice of Pediatric Oncology. 7th ed. Philadelphia Pa: Lippincott Williams & Wilkins; 2016.
National Cancer Institute. Osteosarcoma and Malignant Fibrous Histiocytoma of Bone Treatment (PDQ). 2020. Accessed at https://www.cancer.gov/types/bone/hp/osteosarcoma-treatment-pdq on July 21, 2020.
Wang LL, Gebhardt MC, Rainusso N. Osteosarcoma: Epidemiology, pathogenesis, clinical presentation, diagnosis, and histology. UpToDate. Accessed at www.uptodate.com/contents/osteosarcoma-epidemiology-pathogenesis-clinical-presentation-diagnosis-and-histology on July 21, 2020.
Last Revised: October 8, 2020
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