Ewing's sarcoma overview

# Overview
Ewing's sarcoma is the common name for primitive neuroectodermal tumor. Ewing's sarcoma is the second most common malignant bone tumor in patients younger than 20 years. Ewing's sarcoma is a small round-cell tumor in which cancer cells are found in the bone or in soft tissue. Ewing's sarcoma may occur anywhere in the body, but most commonly occurs in the pelvis and proximal long tubular bones.  The pathogenesis of Ewing's sarcoma includes a t(11;22) chromosomal translocation. On microscopic histopathological analysis, presence of small round cells that have a high nuclear to cytoplasmic ratio, vacuolated cytoplasm, and faded boundaries are characteristic findings of Ewing's sarcoma. There are no established causes for Ewing's sarcoma. The most common symptoms of Ewing's sarcoma include localized bone pain, swelling, fever, loss of appetite, and weight loss. On x-ray, Ewing's sarcoma is characterized by permeative lytic lesion, periosteal reaction, and soft tissue calcification. On MRI, Ewing's sarcoma is characterized by low to intermediate signal on T1, heterogenously high signal intensity on T2, and heterogenous but prominent enhancement on T1 contrast.

# Classification
There is no classification system established for Ewing's sarcoma.

# Pathophysiology
Ewing's sarcoma may occur anywhere in the body, but most commonly in the pelvis and proximal long tubular bones. The pathogenesis of Ewing's sarcoma include t(11;22) chromosomal translocation.  On microscopic histopathological analysis, presence of small round cells that have a high nuclear to cytoplasmic ratio, vacuolated cytoplasm, and faded boundaries are characteristic findings of Ewing's sarcoma.

# Causes
There are no established causes for Ewing's sarcoma.

# Differential Diagnosis
Ewing's sarcoma must be differentiated from osteosarcoma, hematological malignancy, eosinophilic granuloma, and malignant fibrous histiocytoma.

# Epidemiology and Demographics
Ewing's sarcoma is the second most common malignant bone tumor in patients younger than 20 years. Ewing's sarcoma typically occurs in children and adolescents between 10 and 20 years of age.  The overall incidence of Ewing's sarcoma is 0.1 cases per 100,000 individuals. The incidence of Ewing's sarcoma in children aged 10 to 19 years is 1 case for 100,000 individuals. Males are more commonly affected with Ewing's sarcoma than females.

# Risk Factors
Common risk factors in the development of Ewing's sarcoma are age, gender, and race.

# Screening
According to the the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for Ewing's sarcoma.

# Natural History, Complications and Prognosis
Common complications of Ewing's sarcoma include pathologic fracture and metastasis. Pretreatment factors that influence outcome of the Ewing's sarcoma are site of the tumor, size of the tumor, serum LDH levels, and site of metastasis. After administration of preoperative chemotherapy, patients with minimal or no residual viable tumor have a significantly better prognosis than do patients with larger amounts of viable tumor.

# Diagnosis

## Staging
There is no established system for the staging of Ewing's sarcoma.

## History and Symptoms
The most common symptoms of Ewing's sarcoma include localized bone pain, swelling, fever, loss of appetite, and weight loss. The affected bone is not as strong as normal bones and may fracture with minor trauma (a pathological fracture).

## Physical Examination
Common physical examination findings of Ewing's sarcoma are fever, localized swelling, and tenderness at the site of the tumor.

## Laboratory Findings
Laboratory tests for Ewing's sarcoma include complete blood count, erythrocyte sedimentation rate, serum alkaline phosphatase, and lactate dehydrogenase

## Biopsy
Biopsy of Ewing's sarcoma is important for confirming the diagnosis and determining histologic subtype. Biopsy may be performed percutaneously with either a fine-needle, or wide-bore needle, or through a formal incision.

## X Ray
On x-ray, Ewing's sarcoma is characterized by permeative lytic lesion, periosteal reaction, and soft tissue calcification.

## CT
CT scan in Ewing's sarcoma may be helpful in biopsy and staging. CT scan adds little to plain radiography and MRI in direct assessment of the tumor.

## MRI
On MRI, Ewing's sarcoma is characterized by low to intermediate signal on T1, heterogenously high signal intensity on T2, and heterogenous but prominent enhancement on T1 contrast.

## Other imaging findings
Bone scan in Ewing's sarcoma is used to observe abnormal areas of bone and metastasis.

## Other Diagnostic Studies
No additional tests are recommended for the diagnosis of Ewing's sarcoma.

# Treatment

## Medical Therapy
The treatment of Ewing's sarcoma depends on the stage of the tumor. The options are surgery, radiation therapy, chemotherapy, or a combination of these methods. Rather than using the standard staging system, a simpler system is often used when deciding treatment for Ewing's sarcoma. This system divides Ewing's sarcoma of the bone into 2 groups: localized and metastatic.

## Surgery
Surgery in Ewing's sarcoma may be used to remove the tumor following chemotherapy. If necessary, radiation therapy may be used before surgery to help make surgery possible. Surgery may also be used to remove metastases.

## Prevention
There is no established method for the prevention of Ewing's sarcoma.