Ewing Sarcoma

Key Features

Essentials of Diagnosis

• The cardinal signs of bone tumor are pain at the site of involvement, often following slight trauma, mass formation, and fracture through an area of cortical bone destruction

• Second most common malignant tumor of bony origin

• Although most commonly a tumor of bone, it may also occur in soft tissue (extraosseous Ewing sarcoma or peripheral neuroectodermal tumor [PNET])

General Considerations

• Considered a "small, round, blue cell" malignancy

• Accounts for only 30% of primary malignant bone tumors

• Fewer than 200 new cases occur each year in the United States

• Primarily affects white males, almost never affects blacks

• Occurs in toddlers to young adults

Clinical Findings

Symptoms and Signs

• Pain at the site of the primary tumor is the most common presenting sign, with or without swelling and erythema

• Associated symptoms include fevers and weight loss

Differential Diagnosis

• Rhabdomyosarcoma

• Lymphoma

• Neuroblastoma

Diagnosis

Laboratory Findings

• No specific laboratory findings are characteristic

• However, an elevated lactate dehydrogenase may be present

Imaging and Staging

• Radiographs show diaphyses of long bones

• MRI of the primary lesion should be done to define the extent of local disease as precisely as possible

• CT scan of the chest, bone scan, and bilateral bone marrow aspirates and biopsies are all essential to the staging workup

• PET-CT may help monitor therapy response

Diagnostic Procedures

• A biopsy is essential in establishing the diagnosis

• Histologically, Ewing sarcoma consists of sheets of undifferentiated cells with hyperchromatic nuclei, well-defined cell borders, and scanty cytoplasm. Necrosis is common

• Electron microscopy, immunocytochemistry, and cytogenetics may be necessary to confirm the diagnosis

• A generous tissue biopsy specimen is often necessary for diagnosis but should not delay starting chemotherapy

Treatment

• Chemotherapy is started after biopsy and is followed by local control measures

  • Effective chemotherapy uses combinations of dactinomycin, vincristine, doxorubicin, cyclophosphamide, etoposide, and ifosfamide

  • Local measures include surgery, radiation therapy, or a combination of these methods

• Following local control, chemotherapy continues for approximately 6 months

Outcome

Prognosis

• Patients with small localized primary tumors have a 70–75% long-term, disease-free survival rate

• For patients with metastatic disease survival is poor

• Patients with pelvic tumors have about a 50% long-term, disease-free survival

References