Sarcomas are cancers that begin in the body's connective tissues. Sarcomas are often divided into two groups:

  • Bone cancers that begin in the hard part of the bone
  • Soft tissue sarcomas that start in muscle, fat, fibrous tissue, blood vessels, nerves, or other supportive tissues of the body

Osteosarcoma is the most common form of bone cancer in children. 

The tumor usually starts in the faster growing ends of the long bones in the arms and legs. Common places where the tumor is found are the lower end of the thigh bone, the upper end of the shin bone, and the upper end of the long bone of the upper arm. This tumor occurs less often in the jaw, spinal column, shoulder blades and pelvis.

Osteosarcomas are seen more often in boys than girls. It is most often seen in children between the ages of 10 and 20, but it can occur in younger children and adults.