|Classification and external resources|
Micrograph of metastatic Ewing sarcoma (right of image) in normal lung (left of image). PAS stain.
Ewing's sarcoma is a malignant small, round, blue cell tumour. It is a rare disease in which cancer cells are found in the bone or in soft tissue. The most common areas in which it occurs are the pelvis, the femur, the humerus, the ribs and clavicle (collar bone).
Because a common genetic locus is responsible for a large percentage of Ewing's sarcoma and primitive neuroectodermal tumors, these are sometimes grouped together in a category known as the Ewing family of tumors. The diseases are, however, considered to be different: peripheral primitive neuroectodermal tumours are generally not associated with bones, while Ewing sarcomas are most commonly related to bone.
Genetic exchange between chromosomes can cause cells to become cancerous. Most cases of Ewing's sarcoma (85%) are the result of a translocation between chromosomes 11 and 22, which fuses the EWS gene of chromosome 22 to the FLI1 gene of chromosome 11.
EWS/FLI functions as the master regulator.
According to The Bone Cancer Research Trust (BCRT), the most common symptoms are: localized pain, swelling, and sporadic bone pain with variable intensity. The swelling is most likely to be visible if the sarcoma is located on a bone near the surface of the body, but when it occurs in other places deeper in the body, like on the pelvis, it may not be visible.
Clinical findings 
Ewing's sarcoma is more common in males and usually presents in childhood or early adulthood, with a peak between 10 and 20 years of age. It can occur anywhere in the body, but most commonly in the pelvis and proximal long tubular bones, especially around the growth plates. The diaphyses of the femur are the most common sites, followed by the tibia and the humerus. Thirty percent are overtly metastatic at presentation. Patients usually experience extreme bone pain.
Imaging findings 
On conventional radiographs, the most common osseous presentation is a permeative lytic lesion with periosteal reaction. The classic description of lamellated or "onion skin" type periosteal reaction is often associated with this lesion. Plain films add valuable information in the initial evaluation or screening. The wide zone of transition (e.g. permeative) is the most useful plain film characteristic in differentiation of benign versus aggressive or malignant lytic lesions.
MRI should be routinely used in the work-up of malignant tumours. MRI will show the full bony and soft tissue extent and relate the tumour to other nearby anatomic structures (e.g. vessels). Gadolinium contrast is not necessary as it does not give additional information over noncontrast studies, though some current researchers argue that dynamic, contrast enhanced MRI may help determine the amount of necrosis within the tumour, thus help in determining response to treatment prior to surgery.
Bone scintigraphy can also be used to follow tumour response to therapy.
In the group of malignant small round cell tumours which include Ewing's sarcoma, bone lymphoma and small cell osteosarcoma, the cortex may appear almost normal radiographically, while there is permeative growth throughout the Haversian channels. These tumours may be accompanied by a large soft tissue mass while there is almost no visible bone destruction. The radiographs frequently do not shown any signs of cortical destruction.
Radiographically Ewing's Sarcoma presents as "Moth-eaten" destructive radiolucencies of the medulla and erosion of the cortex with expansion.
A grouping of three unrelated teenagers in Wake Forest NC have diagnosed with Ewing's sarcoma. All three children were diagnosed in 2011 and all attended the same temporary classroom together while the school underwent renovation. A fourth teenager living nearby was diagnosed in 2009. The odds of this grouping are considered significant. 
Clinical differential diagnosis 
|This section requires expansion. (February 2013)|
Other entities that may have a similar clinical presentation include osteomyelitis, osteosarcoma (especially telangiectatic osteosarcoma) and eosinophilic granuloma. Soft tissue neoplasms such as pleomorphic undifferentiated sarcoma (malignant fibrous histiocytoma) that erode into adjacent bone may also have a similar appearance.
Ewing's sarcoma is a small round cell tumor, that typically has a clear cytoplasm on H&E staining, due to glycogen. The presence of the glycogen can be demonstrated with positive PAS staining and negative PAS diastase staining. The characteristic immunostain is CD99 which diffusely marks the cell membrane. Morphologic and immunohistochemical findings are corroborated with an associated chromosomal translocation, of which there are several. The most common translocation, present in approximately 90% of Ewing sarcoma cases, is t(11;22)(q24;q12).
Ewing's sarcomas represent 16% of primary bone sarcomas.
Ewing's sarcoma in the United States is most common in the second decade of life, with a rate of 0.3 cases per million in children under 3 years of age, and as high as 4.6 cases per million in adolescents aged 15–19 years. Internationally the annual incidence rate averages less than 2 cases per million children. In the United Kingdom an average of six children per year are diagnosed, mainly males in early stages of puberty. Due to the prevalence of diagnosis during teenage years, there may possibly be a link between the onset of puberty and the early stages of this disease, although no research is currently being conducted to confirm this hypothesis.
Almost all patients require multidrug chemotherapy (often including ifosfamide and etoposide) as well as local disease control with surgery and/or radiation. An aggressive approach is necessary because almost all patients with apparently localized disease at the time of diagnosis actually have asymptomatic metastatic disease.
Treatment often consists of neo-adjuvant chemotherapy, which may include vincristine, doxorubicin, and cyclophosphamide with ifosfamide and etoposide. After about three months of chemotherapy, the remaining tumor is surgically resected, radiated, or both. The surgical resection may involve limb salvage or amputation. Complete excision at the time of biopsy may be performed if malignancy is confirmed at the time it is examined.
Treatment lengths vary depending on location and stage of the disease at diagnosis. Radical chemotherapy may be as short as 6 treatments at 3 week cycles, however most patients will undergo chemotherapy for 6–12 months and radiation therapy for 5–8 weeks. Radiotherapy has been used for localised disease. The tumor has a unique property of being highly sensitive to radiation, sometimes acknowledged by the phrase "melting like snow". But the main drawback is that it recurs dramatically after sometime. Antisense oligodeoxynucleotides have been proposed as possible treatment by down-regulating the expression of the oncogenic fusion protein associated with the development of Ewing's sarcoma resulting from the EWS-ETS gene translocation. In addition, the synthetic retinoid derivative fenretinide (4-hydroxy(phenyl)retinamide) has been reported to induce high levels of cell death in Ewing sarcoma cell lines in vitro and to delay growth of Ewing sarcoma xenografts in vivo mouse models.
Fertility preservation 
In women, chemotherapy may damage the ovaries and cause infertility. To avail for future pregnancies, the woman may preserve oocytes or ovarian tissue by oocyte cryopreservation or ovarian tissue cryopreservation prior to starting chemotherapy. However, the latter may reseed the cancer upon reinsertion of the ovarian tissue. If it is performed, the ovarian tissue should be examined for traces of malignancy at both the pathological and molecular levels prior to the grafting of the cryopreserved tissue.
Staging attempts to distinguish patients with localized from those with metastatic disease. Most commonly, metastases occur in the chest, bone and/or bone marrow. Less common sites include the central nervous system and lymph nodes.
Five-year survival for localized disease is 70% to 80% when treated with chemotherapy. Long term survival for metastatic disease may be less than 10%. However, some sources state it is 25-30%.
Research, information and support 
In the UK and Ireland The Bone Cancer Research Trust (BCRT) funds research and provides information on Ewing sarcoma and other bone cancers. This includes information for teenagers who have this condition.
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See also 
- Cancer.Net: Ewing Family of Tumors, Childhood
- Ewing family of tumors entry in the public domain NCI Dictionary of Cancer Terms