Ewing’s Sarcoma is essentially a primary malignant bone cancer. It is second in its frequency only to osteosarcoma. Yet, it is an infrequent cancer. It is a tumour of neuroectodermal origin. Ewing’s sarcoma is categorized as a small, round-cell tumour classically seen in the bones, rarely in soft tissues, of children and adolescents.
What are the predisposing factors for Ewing’s sarcoma ?
A number of studies have evaluated predisposing factors in Ewing’s Sarcoma.
Patients known to have a familial predisposition to other cancers like gastric cancer or melanoma have been known to have a greater risk of getting Ewing’s sarcoma.
Nevertheless, at this time, there is no absolute evidence that Ewing’s sarcoma is connected with any other disease, familial cancer syndromes, or certain environmental factors.
Where does Ewing’s sarcoma occur ?
Most Ewing’s sarcomas occur in bones. Ewing’s sarcoma has a propensity to affect long tubular bones, especially their shafts, the pelvis, and the ribs but just about any bone can be involved. A majority of 50% of the tumours occur in axial bones, with the most affected bone being the pelvis; a third of the tumours initiate in the lower extremities, and finally, less than 10% are seen occurring in the upper extremities.
In contrast to osteosarcoma, in Ewing’s sarcoma, diaphyseal involvement predominates over metaphyseal disease in the long bones. Metaphyseal tumors comprise of tumours like osteosarcoma, chondrosarcoma and fibrosarcoma.
What are the clinical features of Ewing’s sarcoma ?
It is slightly more common in boys. The most frequent age of diagnosis is the second decade of life. However, cases are known to occur in both the first and third decades as well.
Patients with Ewing’s sarcoma commonly present during the 2nd decade of life; 80% of patients are younger than 18 years of age, and the median age at diagnosis is 14 years. Males are more commonly affected than females.
What is the clinical presentation of Ewing’s sarcoma ?
Firstly, pain is the most common presenting symptom in patients with Ewing’s sarcoma; it can either be local or regional. Pain can be continuous or discontinuous and is highly variable. Pain may be accompanied by altered sensation in some cases.
As the majority of Ewing’s sarcoma patients are in their growing period, the pain can frequently be wrongly diagnosed as bony growth or sports injuries.
Secondly, a palpable mass or a swelling following pain can be seen. It is tumour growth which causes this mass or swelling. The tumour bulk, however, may be unapparent for a long time in patients with tumours in the pelvis, chest or in the femur (thigh bone).
The duration of symptoms can vary from weeks to months, or rarely even years.
The symptoms basically depend on the site of occurrence.
Non-specific symptoms like slight or moderate fever are seen more commonly in more advanced stages or metastatic stages.
How is Ewing’s sarcoma diagnosed ?
Pain without causative trauma, lasting for longer than a month, which continues even at night, should initiate early imaging and diagnosis.
In laboratory investigations, neither blood, serum, nor urine test can recognize Ewing’s sarcoma, in particular. All the nonspecific signs of tumour or inflammation may be noted- an elevated erythrocyte sedimentation rate, anaemia and/or leukocytosis. Elevated levels of serum lactate dehydrogenase draw a parallel with tumour burden and, so it is associated with inferior outcome. Serum and urine catecholamine levels are always in the normal range.
Radiologically, bone destruction in and around the site of tumour, and separation of the periosteum (outer layer) from the rest of the bone (Codman triangle) point to features of a malignant bone tumour.
Osteomyelitis looks similar to Ewing’s sarcoma on conventional radiography. The tumour in Ewing’s sarcoma occurs in the diaphysis, mostly.
However, magnetic resonance imaging gives the most accurate local extent of disease in the bone and the relationship of the lesion to adjacent vital structures like blood vessels and nerves.
Computed tomography scan and the less common, fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) are the best methods for the recognition of bone metastases in Ewing’s sarcoma.
What is the Pathology and Molecular Pathology for Ewing’s sarcoma ?
As for other malignant diseases, the authoritative diagnostic test is the classical biopsy. Open biopsy (surgical removal of tissue from tumour site) is the best for diagnosis. After that, the tissue is fixed, stained and examined under the microscope.
Histologic features of Ewing’s sarcoma
Classic Ewing’s sarcoma, as first described by James Ewing in 1921 is composed of similar looking population of small, uniform round cells with malignant cellular features, arranged in sheets. True rosette structures may be identified occasionally.
Immunohistochemical features of Ewing’s sarcoma
Strong expression is seen of the cell-surface glycoprotein- CD99. This is diagnostic of Ewing’s sarcoma.
Cytogenetic features of Ewing’s sarcoma
Ewing’s sarcoma is characterized by a comparatively straightforward karyotype. A reciprocal chromosomal translocation is seen between chromosomes 11 and 22, the t(11;22)(q24;q12). This translocation is present in a majority of tumours and is therefore considered pathognomonic for the disease.
How do we stage Ewing’s sarcoma ?
At the time of presentation, staging has to include a complete search for metastases. Metastasis is seen in about a quarter of affected patients. Primary metastases can be seen in either the lungs, bone, bone marrow, or possibly in all or combinations. Neighbouring metastasis to lymph nodes or distant metastases to sites like the liver or other organs are rare.
What is the treatment for Ewing’s sarcoma ?
With the advent of recent multipronged therapeutic regimens such as combination chemotherapy, surgery, and/or radiotherapy, cure rates of 50% and more can be achieved. The treatment of Ewing’s sarcoma patients is being ordered in cooperative trials, in order to enhance and improve treatment outcome further.
Earlier, radiotherapy was regarded as the gold standard. Now, cure from Ewing’s sarcoma can only be achieved with both chemotherapy and local control. Present treatment schedules advocate primary induction chemotherapy first, then local therapy and finally, adjuvant chemotherapy. Local control is done by contemporary orthopedic surgery. It is designed to preserve function and improve limb salvage rates without decreasing survival rates. An interdisciplinary approach involving all the field experts is necessary.
What is the prognosis for Ewing’s sarcoma ?
Ewing’s sarcoma has retained the most unfavourable prognosis of all primary musculoskeletal tumors. Before multi-drug chemotherapy, the long-term survival rates were less than 10%. The development of multi-disciplinary therapy with all three regimens, that is chemotherapy, radiation, and surgery has greatly increased long-term survival rates to greater than 50%.
The presence of metastatic disease is the most unfavourable prognostic feature.
At the time of diagnosis, those with isolated lung metastases have a slightly superior outcome (roughly 30% survive) as compared to those with bone or marrow metastases (20% or even less).
Children less than 10 years of age fare better than grown-up patients.
Size at the time of diagnosis also determines prognosis. Patients with large lesions have a lesser chance of survival.
Chromosomal changes also are of prognostic importance, and the presence of reciprocal translocations and additional cytogenetic changes may carry adverse prognosis. The disease’s response to initial therapy can foretell outcome, too.
What is the rate of recurrence ?
Patients with primary disease with metastasis have higher chances for relapse than those with only localized disease. After recurrence, the probability of long-term survival is less than 20%–25%.
The timing and type of recurrence are important prognostic factors. Patients with relapse, early on, after initial diagnosis, have a poorer prognosis. Those with later recurrence have a better survival probability.
Treatment strategies should be modified according to each individual case. In patients with suspected recurrence, treatment should be more aggressive.
Advances in the biology of Ewing’s sarcoma have led to increased understanding of the fundamental molecular basis of the disease, and this will hopefully lead to better therapeutic approaches for the disease.
How to find and reach cancer specialists for the treatment of Ewing’s sarcoma ?
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Disclaimer: The content provided here is meant for general informational purposes only and hence SHOULD NOT be relied upon as a substitute for sound professional medical advice, care or evaluation by a qualified doctor/physician or other relevantly qualified healthcare provider.
