Sarcoma is cancer that develops in the tissues that support and connect parts of the body. These include bone, fat, muscle, and soft tissue. Cancer begins when healthy cells change and grow uncontrollably. They form a mass called a tumor. A tumor can be cancerous or benign. A cancerous tumor is malignant. This means that it can spread to other parts of the body. A benign tumor means the tumor will not spread.
Osteosarcoma is a cancer of the bone that destroys tissue and weakens the bone. It develops from immature bone cells that normally form new bone tissue.
Places osteosarcoma begins
It most often starts in the bones around the knee joint, either at the femur, which is the lower end of the thigh bone, or the tibia, which the upper end of the shin bone. The next most common place osteosarcoma begins is in the humerus. This is the upper arm bone close to the shoulder.
However, osteosarcoma can develop in any bone in the body. Rarely, it occurs as a tumor in the body’s soft tissue, outside the bone.
Types and subtypes of osteosarcoma
Medullary tumor, also called a central tumor
Peripheral tumor, also called a surface tumor
Each has different subtypes. The type and subtype of osteosarcoma is determined 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. They each account for less than 5% of all osteosarcomas.
Medullary osteosarcoma subtypes:
Conventional central osteosarcoma
Intraosseous well-differentiated, or low-grade, osteosarcoma
Small cell osteosarcoma
Peripheral osteosarcoma subtypes:
Parosteal, well-differentiated or low-grade, osteosarcoma. Also called juxtacortical osteosarcoma.
Periosteal osteosarcoma that is low grade to intermediate grade
High-grade surface osteosarcoma
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