What are the diagnostic tests and next steps for neuroblastoma?

Diagnostic Testing and Next Steps for Neuroblastoma

The diagnosis of neuroblastoma requires either tissue biopsy with histologic confirmation OR bone marrow aspirate/biopsy showing unequivocal tumor cells plus elevated urine catecholamines, followed by comprehensive staging with cross-sectional imaging (CT or MRI) and 123I-MIBG scintigraphy to assess for metastatic disease. 1

Diagnostic Criteria

Two pathways exist for definitive diagnosis 1:

1. Unequivocal pathologic diagnosis from tumor tissue by light microscopy, OR
2. Bone marrow aspirate/trephine biopsy containing unequivocal tumor cells (syncytia or immunocytologically positive clumps) PLUS elevated urinary catecholamine metabolites

Initial Tissue Sampling Approach

For Localized Disease

• Surgical resection should be considered first, particularly when image-defined risk factors (IDRFs) are absent 1
• When biopsy is indicated: obtain at least 10 cores (ideally 20-30 mm length using 16-gauge needle) or incisional biopsy >1 cm³ 1
• Multiple core biopsies may suffice, but adequate tissue for histologic AND molecular evaluation is crucial 1
• Fine-needle aspiration is NOT recommended 1

For Suspected Metastatic Disease

• Bilateral bone marrow aspirates and trephine biopsies can establish diagnosis when marrow is the only tumor source 1
• Ensure adequate material for complete molecular testing 1

Special Populations Where Biopsy Should Be Deferred

• Infants <2 months with hepatomegaly 1
• Infants <6 months with L1 adrenal tumors ≤3.1 cm (solid) or ≤5 cm (≥25% cystic) 1
• Patients with coagulopathy or impending organ failure 1

Essential Laboratory Testing

Required for All Patients 1

• Complete blood count with differential
• Comprehensive metabolic panel
• Urine catecholamines (HVA and VMA) - elevated in majority of patients; required for diagnosis only if bone marrow is sole diagnostic tissue 1

Additional Laboratory Tests (Selected Cases) 1

• Lactate dehydrogenase and ferritin (prognostic markers, though not part of risk classification)
• Prothrombin/INR if liver involvement or bleeding concern
• Pregnancy test for patients of childbearing potential

Pre-Treatment Assessments (If Specific Chemotherapy Planned) 1

• Audiogram
• Echocardiogram or electrocardiogram

Imaging Protocol

Cross-Sectional Imaging for Local Disease 1

Primary evaluation requires:

• MRI with/without contrast OR CT with contrast to evaluate soft tissue disease
• MRI spine with/without contrast for paraspinal disease or concerns about nerve root/spinal cord involvement
• MRI brain with/without contrast OR CT skull/orbits with contrast if neurologic symptoms present

Metastatic Disease Assessment 1

123I-MIBG scintigraphy is the primary metastatic imaging modality:

• High specificity and sensitivity (uptake in up to 90% of neuroblastomas) 1
• Use modified Curie score for semi-quantitative assessment in North America 1
• SPECT or SPECT/CT should be performed at known/suspected disease sites when available for improved sensitivity 1

18F-FDG-PET imaging indications:

• MIBG-nonavid disease or suspected mixed-avidity disease 1
• Exception: infants <6 months with small L1 adrenal tumors (criteria above) 1
• Alternative/supplemental tool when MIBG and anatomic imaging don't correlate 1

Molecular and Histologic Evaluation

Pathology Requirements 1

• Histologic classification per International Neuroblastoma Pathology Classification (INPC) prior to therapy initiation
• Immunohistochemical staining for small samples or undifferentiated subtypes:
  • Chromogranin and synaptophysin (neuroendocrine markers) 1
  • PHOX2B (strongly recommended neural crest marker) 1
  • Tyrosine hydroxylase 1

Molecular Testing 1

• Assessment of MYCN amplification, segmental chromosomal aberrations, and ALK status is essential
• Single robust assay covering neuroblastoma-associated genes preferred when tissue limited 1
• Fluorescence in situ hybridization, microarray, or flow cytometry can assess prognostic biomarkers but won't identify sequence variants in genes like ALK 1

Next Steps After Diagnosis

Staging 1

• Use International Neuroblastoma Risk Group (INRG) Staging System before treatment initiation
• Localized tumors classified by number of IDRFs present 1
• Complete staging before treatment when possible; emergent therapy should not be delayed for MIBG/FDG-PET, but obtain imaging as soon as possible 1

Risk Classification 1

• Tumor stage, age, histology, MYCN status, and chromosomal aberrations determine risk group
• Risk classification guides treatment intensity and approach 1

Clinical Pitfalls to Avoid

• Do not use fine-needle aspiration - insufficient tissue for complete evaluation 1
• Ensure experienced pathologist reviews frozen sections to confirm specimen adequacy, as samples may be necrotic 1
• Bilateral bone marrow biopsies alone may not suffice for INPC characteristics assessment 1
• Plan tissue requirements in advance (formalin-fixed, fresh, frozen) to ensure all testing completed 1