Definition of Ewing's sarcoma:

Ewing's sarcoma is a malignant (cancerous) bone tumor that affects children.

Causes, incidence, and risk factors:

Ewing's sarcoma can occur any time during childhood and young adulthood, but usually develops during puberty, when bones are growing rapidly. It is 10 times as common in Caucasian children as in African-American, African, and Asian children.

The tumor may arise anywhere in the body, usually in the long bones of the arms and legs, the pelvis, or the chest. It may also develop in the skull or the flat bones of the trunk.

The tumor often spreads (metastasis) to the lungs and other bones. Metastasis at the time of diagnosis is present in approximately one-third of children with Ewing's sarcoma. Rarely, Ewing's sarcoma can occur in adults.