What are the investigation steps for Ewing's sarcoma?

Investigation Steps for Ewing's Sarcoma

Patients with radiological findings suggesting Ewing's sarcoma should be immediately referred to a specialized bone sarcoma center for proper diagnosis and management without prior biopsy. 1

Initial Diagnostic Evaluation

• Radiological assessment: Complete evaluation of the entire affected bone should be performed before any biopsy 1
• Biopsy: Histological diagnosis is made by needle biopsy or open surgical biopsy at a specialized center 1
• Immunohistochemistry: Ewing's sarcoma can be distinguished from other pediatric "blue tumors" by expression of the MIC2 gene 1
• Molecular testing: Detection of characteristic translocations involving the EWS gene (most commonly t(11;22)(q24;q12), but also t(21;22)(q22;q12)) by cytogenetics or PCR is diagnostic and present in >90% of cases 1, 2

Staging and Risk Assessment

• Pulmonary metastasis evaluation: Computed tomography of the chest to detect lung metastases 1, 3
• Bone metastasis evaluation: Bone scintigraphy to investigate potential bone metastases 1, 3
• Bone marrow assessment: Bone marrow aspirates are mandatory for light microscopy examination 1
• Fertility preservation: Sperm banking should be considered before initiating treatment 1

Prognostic Factor Assessment

• Tumor size: Document tumor diameter (>8-10 cm indicates worse prognosis) 1, 3
• Tumor location: Note if tumor is in pelvic region (indicates worse prognosis) 1, 3
• Age assessment: Document patient age (>15 years indicates worse prognosis) 1, 3
• Laboratory tests: Measure serum lactate dehydrogenase (elevated levels indicate worse prognosis) 1, 3
• Metastatic status: Approximately 20% of patients have detectable metastases at diagnosis, most commonly in lungs and/or bone/bone marrow 1

Treatment Planning Considerations

• Multidisciplinary approach: Treatment should be coordinated by a specialized center with expertise in Ewing's sarcoma 1, 3
• Chemotherapy planning: Prepare for combination chemotherapy including doxorubicin, vincristine, ifosfamide, etoposide, dactinomycin, and cyclophosphamide 1, 3
• Local therapy assessment: Evaluate feasibility of surgery versus radiotherapy based on tumor location and extent 1
• Response monitoring: Plan for assessment of histological response to preoperative chemotherapy 1, 3

Common Pitfalls and Caveats

• Delayed referral: Patients with suspected bone sarcomas should be referred to specialized centers without prior biopsy to avoid contamination of tissue planes 1
• Inadequate staging: Failure to perform complete metastatic workup can lead to inappropriate treatment planning 1
• Improper biopsy technique: Poorly planned biopsies can compromise subsequent surgical management 1
• Underestimating the importance of molecular diagnosis: Molecular confirmation of EWS gene rearrangements is essential for definitive diagnosis 1, 2
• Delayed local therapy: Delay in any form of local control beyond 4 months can negatively impact outcomes 4

Following these investigation steps in a systematic manner is crucial for accurate diagnosis, appropriate staging, and optimal treatment planning for patients with Ewing's sarcoma, ultimately improving morbidity, mortality, and quality of life outcomes.