Neuroblastoma

Quick Answer

Neuroblastoma is the paradigm pediatric MIBG-avid tumor: I-123-MIBG (whole-body ± SPECT/CT) is central to staging, response assessment, and confirming avidity before I-131-MIBG therapy. Disease extent is quantified with the Curie or SIOPEN semiquantitative scores, which carry prognostic and response weight. Thyroid blockade with stable iodine is mandatory. For the minority of MIBG-non-avid tumors, FDG-PET or Ga-68-DOTATATE (somatostatin-receptor) imaging localizes disease.

Background & Pathophysiology

Neuroblastoma is a sympathetic nervous system tumor of neural-crest origin (adrenal medulla or paraspinal ganglia), the most common extracranial solid tumor of childhood. Because tumor cells share the norepinephrine transporter (NET/uptake-1), they concentrate MIBG — the basis of both imaging and therapy. Risk stratification integrates age, stage (INRG), MYCN amplification, histology, and DNA ploidy.

Clinical & Laboratory

Abdominal mass, bone/marrow disease, periorbital ecchymoses ("raccoon eyes"), and paraneoplastic opsoclonus-myoclonus. Urine catecholamine metabolites (HVA, VMA) are elevated in most cases and support diagnosis/surveillance. MYCN amplification is the key adverse molecular marker.

Imaging Role

• Staging & response: I-123-MIBG maps primary, nodal, marrow, and skeletal disease; serial scoring tracks response to induction chemotherapy.
• Scoring: the Curie score (9 body segments + soft tissue) and the SIOPEN score (12 skeletal segments) grade skeletal MIBG burden; the post-induction score is prognostic.
• Theranostic gate: documented MIBG avidity selects patients for I-131-MIBG therapy in relapsed/refractory high-risk disease.
• MIBG-negative disease: FDG-PET or Ga-68-DOTATATE-PET localizes non-avid tumor (DOTATATE also opens a PRRT option).

Preparation & Technique

• Thyroid blockade with stable iodine (e.g., potassium iodide) starting before and continuing after MIBG — protects the thyroid from free radioiodine.
• Discontinue interfering drugs (labetalol and many antihypertensives, sympathomimetics, tricyclics) that block NET uptake.
• SPECT/CT improves localization and scoring accuracy.

Interpretation & Decision

A falling Curie/SIOPEN score with induction predicts better outcome and informs therapy intensification. Physiologic uptake (salivary, myocardium, brown fat, liver, bowel, adrenal) must be distinguished from disease. A negative diagnostic scan does not exclude disease — post-therapy scans (higher activity) and complementary FDG/DOTATATE catch non-avid sites.

Differential Diagnosis

Other pediatric small-round-blue-cell tumors, ganglioneuroma/ganglioneuroblastoma (mature end of the spectrum), pheochromocytoma/paraganglioma (also MIBG-avid), and physiologic MIBG uptake mistaken for tumor.

Reporting Checklist

• Report the Curie/SIOPEN score and disease sites; compare with prior for response.
• Confirm thyroid blockade and interfering-drug discontinuation.
• State MIBG avidity (theranostic candidacy) or recommend FDG/DOTATATE if non-avid.
• Attribute physiologic uptake explicitly.

Common Pitfalls

• Interfering medications (many antihypertensives, sympathomimetics, tricyclics) reducing MIBG uptake.
• Physiologic uptake (salivary, myocardium, brown fat, bowel, adrenal) misread as disease.
• Inadequate thyroid blockade producing thyroid/stomach activity (and thyroid dose).
• Treating a negative diagnostic scan as excluding disease.

Board Pearls

Neuroblastoma is the paradigm MIBG-avid pediatric tumor (uptake via the norepinephrine transporter): I-123-MIBG (± SPECT/CT) is central to staging, response, and confirming avidity before I-131-MIBG therapy (the theranostic gate in relapsed/refractory high-risk disease). Skeletal burden is scored by Curie (9 segments + soft tissue) or SIOPEN (12 skeletal segments) — a falling post-induction score is prognostic.

Thyroid blockade with stable iodine is mandatory before MIBG, and interfering drugs (many antihypertensives, sympathomimetics, tricyclics) must be stopped or uptake falls. For MIBG-non-avid tumors, FDG-PET or Ga-68-DOTATATE finds disease a diagnostic MIBG scan would miss.

A negative diagnostic scan does not exclude disease — post-therapy (higher-activity) scans and complementary tracers catch non-avid sites. MYCN amplification is the key adverse marker driving high-risk classification. DOTATATE positivity additionally opens a PRRT pathway in selected cases.

Related Pages

• Tracer: I-123-MIBG; therapy: I-131-MIBG; disease: Neuroendocrine tumors.

Figure / Diagram Suggestions

• A Curie vs SIOPEN scoring-region diagram.
• A NET-uptake / thyroid-blockade mechanism cartoon.
• A MIBG-avid vs MIBG-negative (FDG/DOTATATE) decision path.

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