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Sarcoma is cancer that develops in the tissues that support and connect parts of the body, including bone, fat, muscle, and soft tissue. Cancer begins when normal cells change and grow uncontrollably, forming a mass called a tumor. A tumor can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body).
Osteosarcoma is a cancer of the bone that destroys tissue and weakens the bone. Osteosarcoma starts in immature bone cells that normally form new bone tissue. Rarely, it can also occur as a tumor in the soft tissues of the body, outside the bone.
Osteosarcoma most often starts in the bones around the knee joint, at the lower end of the femur (thigh bone) or the upper end of the tibia (shin bone). The second most common place is in the humerus (upper arm bone close to the shoulder). However, osteosarcoma can develop in any bone in the body.
Osteosarcoma is described as either a medullary (central) tumor or a peripheral (surface) tumor. Each has different subtypes. The type and subtype of osteosarcoma is identified by looking at the tumor cells through a microscope. The most common subtype is called conventional central osteosarcoma. The other subtypes are much less common, each accounting for less than 5% of all osteosarcomas.
Medullary osteosarcoma subtypes include:
- Conventional central osteosarcoma
- Telangiectatic osteosarcoma
- Intraosseous well-differentiated (low-grade) osteosarcoma
- Small cell osteosarcoma
Peripheral osteosarcoma subtypes include:
- Parosteal (juxtacortical) well-differentiated (low-grade) osteosarcoma
- Periosteal (low-grade to intermediate-grade) osteosarcoma
- High-grade surface osteosarcoma
Find out more about basic cancer terms used in this section.
Looking for More of an Overview?
If you would like additional introductory information, explore these related items on Cancer.Net:
- ASCO Answers Fact Sheet: Read a one-page fact sheet (available in PDF) that offers an easy-to-print introduction for this type of cancer.
- Cancer.Net Patient Education Video: View a short video led by an ASCO expert in childhood cancer that provides basic information and areas of research
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