Ewing Sarcoma
Submitted by Christina Kang, MSIV

General Considerations 

• Second most common malignant bone tumor in children (after osteosarcoma)
• Accounts for approximately one-third of all primary bone tumors
• More common in males than females
  • More common in Caucasians
• Occurs between the ages of 5-30 years
  • Highest frequency between 5-15 years
• Rare over age 30
• Location
• Arise in medullary cavity, usually of long bones in the lower extremities
• Most commonly occurs in long bones and pelvis
• Most occur in femur, pelvis, tibia, and humerus
• But they can occur in virtually any bone
• Commonly involves metadiaphysis of long bones 

Clinical Findings

• Most common symptoms are localized pain and swelling
• Additional symptoms may include
  • Fever
• Weight loss
• Anemia
• Leukocytosis
• Elevated erythrocyte sedimentation rate 

Imaging Findings

• Most lesions are visible on conventional radiographs
  • However, their degree of spread is better evaluated with MRI
• Common manifestations on conventional radiography include
  • Poorly marginated, lytic, destructive lesion
• Permeative (small holes) or moth-eaten (mottled) appearance
• Rarely, they can be sclerotic
• Soft tissue mass or infiltration is common
• Soft tissue mass may occur without destruction of cortex
• Soft tissue mass may produce saucerization (scalloped depression in cortex)
• Periosteal reaction is common
• Lamellated - onion-skinning due to successive layers of periosteal development
• Sunburst or spiculated - hair-on-end appearance when new bone is laid down perpendicular to cortex along Sharpey’s fibers
• Codman’s triangle - formed between elevated periosteum with central destruction of cortex
• Osteosclerosis may be present secondary to reactive bone formation
• Other, less common, manifestations
• Thickened cortex
• Expansion of bone
• Pathologic fractures
• Radioisotope Bone Scan
• Increased uptake in areas of bone destruction
• Whole-body bone scans are used to detect metastatic lesions
• Metastases may be present in up to 30% of cases at time of diagnosis
• CT
• To evaluate bone destruction and extra-osseous involvement
• MRI
• Method of choice for tumor staging
• Assesses soft tissue involvement
• Low signal intensity on T1WI
• Heterogeneous gadolinium enhancement
• High signal intensity on T2WI
• Evaluates response to chemotherapy and radiation treatment 

Differential Diagnosis

• Ewing sarcoma is one of the small, round cell lesions of bone, including
• Neuroblastoma
• Histiocytosis X
• Leukemia
• Reticulum cell sarcoma
• Multiple myeloma
• Age and skeletal location may be important factors in narrowing the differential diagnosis
• Osteomyelitis
• Shorter duration of pain and less aggressive periosteal reaction than Ewing’s
• Eosinophilic granuloma
• Benign bone lesion with solid periosteal reaction
• Osteosarcoma
• Commonly occurs in long bones of young patients
• Homogeneous, cloudlike osteoid deposition in soft tissues
• Lymphoma
• Older age range
• Clinically healthy 

Prognosis

• 60-75% five-year survival
• Predictors of poorer prognosis
  • Large tumors
• Non-resectable lesions, such as those in the pelvis
• Older age
• Elevated leukocyte count and sedimentation rate at presentation