Ewing's Sarcoma And PNET

What Is It?

Ewing's sarcoma is a very rare solid tumor that occurs most often in adolescents and children, although it can occur in adults as well. Although Ewing's sarcoma develops within bones and formerly was considered to be a bone cancer, it actually arises from a type of primitive nerve cell. For this reason, Ewing's sarcoma can occur in the body's soft tissues as well. PNET is the shortened way of referring to a similar tumor called primitive neuroectodermal tumor. It also is known as peripheral neuroepithelioma. While they were previously described as separate cancers, it is now thought that Ewing's sarcoma and PNET represent different types of the same cancer. Their treatment and response to therapy are similar. Askin's tumor is the name given to PNET tumors of the chest wall.

Ewing's sarcoma usually develops in the arms or legs, but sometimes it occurs in the pelvis, ribs, spine and, in rare cases, other bones or soft tissues. At the time of diagnosis, about 23 percent to 26 percent of Ewing's sarcomas have already spread (metastasized) to another site, usually to the lungs, a second bone or the bone marrow.

Like other cancers, Ewing's sarcoma is made up of abnormal cells that multiply out of control. The cells of Ewing's sarcoma show a changed pattern of DNA. This change, called a translocation, usually involves a rearrangement of DNA pieces between chromosome 22 and chromosome 11. The reason for this chromosome problem is a mystery. The genetic problem is not inherited. It develops after birth. There is no evidence that this cancer is related to exposure to radiation, chemicals or any other environmental factor. Ewing's sarcoma is very rare, with an average of only 150 new cases reported per year in the United States. It is almost always a tumor of childhood or adolescence, with 64 percent of cases occurring in people between the ages of 10 and 20 and 27 percent before age 10. Only 9 percent of people with Ewing's sarcoma are adults, usually between the ages of 20 and 30. About 96 percent of people with this cancer are white.

Symptoms

Symptoms of Ewing's sarcoma include:

• Persistent pain and swelling in an arm or leg, which may occur at rest and may even awaken the patient from sleep
• A firm lump on an arm or leg, sometimes with local tenderness
• A limp, if the tumor affects the leg
• Difficulty breathing, if the tumor affects the ribs
• Fever (in 28 percent of patients)
• Weight loss

In physically active or competitive children, the pain and swelling of Ewing's sarcoma can be mistaken for symptoms of a sports injury. In patients who have a fever, symptoms of Ewing's sarcoma often are confused with those of osteomyelitis (bone infection).