What is Ewing sarcoma?
Ewing sarcoma is a cancer that occurs primarily in the bone or soft tissue. Ewing sarcoma can occur in any bone, but most often it is found in the long bones such as the femur (thigh), tibia (shin), or humerus (upper arm). It can involve the muscle and the soft tissues around the tumor site as well. Ewing sarcoma cells can also spread (metastasize) to other areas of the body including the bone marrow, lungs, kidneys, heart, adrenal gland, and other soft tissues.
Ewing sarcoma accounts for about 2 percent to 3 percent of childhood cancers. About 250 children and adolescents will be diagnosed with Ewing sarcoma in the US. It is the second most common malignant bone tumor in children and adolescents. Ewing sarcoma most often occurs in children between the ages of ten and 20. More males are affected than females.
What causes Ewing sarcoma?
The exact cause of Ewing sarcoma is not fully understood. There seems to be no known risk factors or prevention measures available. However, researchers have discovered chromosomal changes in a cell's DNA that can lead to Ewing sarcoma formation. These changes are not inherited. They develop in children after they are born for no apparent reason.
In nearly 85 percent of these cases, the change involved the fusing of genetic material between chromosomes #11 and #22. When a certain piece of chromosome #11 is placed next to the EWS gene on chromosome #22, the EWS gene gets "switched on." This activation leads to an overgrowth of the cells and eventually the development of cancer. The exact mechanism remains unclear, but this important discovery has led to improvements in diagnosing Ewing sarcoma.
Some physicians classify Ewing sarcoma as a primitive neuroectodermal tumor (PNET). This means the tumor may have started in fetal, or embryonic, tissue that has developed into nerve tissue.