II. Epidemiology

  1. Incidence: One in 100,000 aged 10 to 19 years old
    1. Second most common Bone Cancer (Osteosarcoma is most common)
    2. Accounts for one third of U.S. Bone Cancer cases
  2. Race
    1. Rare in black children (contrast with Osteosarcoma)
    2. More common in white and asian patients
  3. Age
    1. Median onset age 15 years old
  4. Gender
    1. Slightly more common in males

III. Risk Factors

  1. Chromosome 11 and 22 translocation (95% of cases)
  2. Chromosome 21 and 22 translocation (5-10% of cases)

IV. Types: Ewing Sarcoma Family of Tumors

  1. Ewing Sarcoma of Bone and Soft Tissue
  2. Peripheral Primitive Neuroectodermal Tumor (PPNET)
  3. Askin Tumors (primary chest wall tumors)
    1. When large, may interfere with breathing

V. Pathophysiology

  1. Small round cell undifferentiated tumor
    1. Likely derives from primitive neuroectodermal and neural crest cells or possibly stem cells
    2. Grouped with other blue round cell tumors (based on histology)
  2. Associated with Chromosome translocation t(11,22)
  3. Primary tumor distribution
    1. Pelvis (most common)
    2. Femoral diaphysis
    3. Tibia diaphysis
    4. Humerus diaphysis
    5. Ribs
    6. Scapula
  4. Metastatic locations
    1. Lungs
    2. Other bones

VI. Symptoms

  1. Pain and swelling limits range of motion of joint
  2. Constitutional (Fever, Weight loss)
  3. May present as Pediatric Limp

VII. Imaging

  1. XRay (may be normal)
    1. Bone destruction (75% of cases)
    2. Soft tissue extension (64% of cases)
    3. Reactive bone formation (25%)
    4. Classic onion-skinning appearance (lamellated periosteal reaction) in 23% of cases
    5. Sunburst pattern (radiating calcification) in 20% of cases
  2. MRI of lesion
    1. Defines extent of tumor involvement

VIII. Differential Diagnosis

  1. Osteosarcoma
  2. Osteomyelitis
  3. Rhabdomyosarcoma (if soft tissue lesion)
  4. Primary Lymphoma involving bone
  5. Langerhans Cell Histiocytosis
  6. Metastatic Neuroblastoma

IX. Evaluation

  1. Biopsy by surgeon or CT-guided biopsy
  2. Imaging to identify metastases
    1. Chest CT
    2. Bone scan
    3. Bone Marrow Biopsy

X. Management

  1. Surgical Excision with clear margin excision
  2. Chemotherapy (neoadjuvant before surgery and adjuvant after surgery)
    1. Cyclophosphamide
    2. Doxorubicin
    3. Etoposide
    4. Ifosamide
    5. Vincristine
  3. Radiation Therapy Indications (contrast with Osteosarcoma, in which radiation is not used)
    1. Lung metastases
    2. Palliative Care
    3. Paraspinal tumors with neurologic compromise
    4. Positive margins on resection
    5. Unresectable tumor

XI. Prognosis

  1. Small, distal, localized tumors: 75% cure
  2. See Osteosarcoma for positive and negative prognostic factors
    1. Osteosarcoma share the same prognostic factors
    2. Pelvic tumors are also associated with worse prognosis

XII. Follow-up: Careful and long-term observation

  1. Relapse may occur even a decade after diagnosis
  2. Cardiotoxicity due to Chemotherapy (Anthracycline)
  3. Secondary malignancy (e.g. Osteosarcoma)
    1. Especially if radiation used

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