Ewing's sarcoma is a cancer. The cancer can start in bone or in soft tissues. The most common sites for Ewing's sarcoma are the pelvis, the thigh, and the trunk of the body. The peak ages are between 10 and 20, but younger children and older adults can also get Ewing's sarcoma. We do not know exactly what kind of cell gives rise to Ewing's sarcoma. It has some features that resemble the early cells that would normally develop into part of the nervous system. We do not know what causes Ewing's sarcoma. The most common early signs of Ewing's sarcoma are pain and swelling. Like other sarcomas, Ewing's sarcoma can spread to other parts of the body. Even when the tumour is detected at a very small size, there may be evidence of microscopic spread. For this reason, Ewing's sarcoma always requires treatment to the whole body. This treatment includes chemotherapy. Chemotherapy is intended to destroy the tumour cells which have spread to the rest of the body and to shrink the main mass of tumour cells. Successful treatment also requires another form of treatment to the main mass of tumour. This can be surgery, radiation therapy, or a combination of the two.
In young people, the development of the tumour appears to be in some way related to periods in life with rapid growth, hence the average for tumour development is 14-15 years. The relationship to growth may also be part of the explanation why Ewing's sarcoma is slightly more common in boys than in girls. However, Ewing's sarcoma remains an extremely rare tumour in all groups of the population, and there is no extra cause for concern in rapidly growing teenagers. The relationship between bone growth and Ewing's sarcoma is thought to be due to an increased vulnerability of rapidly growing cells to damage caused by chance or by as yet unidentified factors.
Ewing's sarcoma spreads when tumour cells enter the blood supply and are circulated to other parts of the body where they may form secondary tumours ("metastases"). Chemotherapy is given to kill these circulating tumour cells. The most common sites for secondary tumours are the lungs and other bones. Tumour cells may also spread via the lymphatic system (this is a network of lymph glands around the body). Also, tumours can spread by direct growth of the primary tumour to form "skip metastases", though these are rare.
Delays in diagnosis of Ewing's sarcoma are extremely common. The average duration of symptoms is 20 weeks and for patients with tumours of the pelvis it is not uncommon for patients to have had symptoms for one year or more.
The first symptoms experienced by most patients are rather non-specific pain which gradually becomes more severe and persistent. Many patients will have been investigated for a variety of conditions and some will have had treatment including operations which have not resolved the problem. Up to 25% of patients will have had an X-ray which has either not been of the right part of the bone or has failed to detect the abnormality in its early stages.
No-one has ever proven that an actual delay in diagnosis has directly affected prognosis for Ewing's sarcoma. This is somewhat surprising as tumour size has been shown to be associated with overall survival in that smaller tumours tend to have a better outlook. The link between tumour size and duration of symptoms is however not clear. some patients will present very late with small tumours, whilst others will have a very short history and yet have a very large tumour.
Whilst tumour size is an important prognostic factor the actual responsiveness to chemotherapy is probably more important and this is not necessarily related to tumour size in any way. Some tumours will always be sensitive to chemotherapy, whilst others will not.
The presence of metastatic disease is another poor prognostic factor and whilst metastases are more common in large tumours, there is no clear cut relationship that identifies when metastases will be released and become detectable. Sometimes the person with Ewing's sarcoma or the parents relate a previous injury or trauma to the development of the tumour. However, medical research has not found any proven relationship between such injury and the risk of subsequently developing Ewing's sarcoma .