Introduction And Epidemiology
- Most common extracranial solid tumor in children.
- Accounts for 6-10% of all childhood malignancies.
- Most commonly diagnosed malignancy in first year of life.
- Annual incidence: 10 per million live births.
- Median age at diagnosis: 18-19 months.
- Age distribution: 50% under 2 years, 75% under 4 years, 90% under 10 years.
- Peak incidence occurs at 2 years of age.
- Originates from primordial neural crest cells destined for adrenal medulla and sympathetic ganglia.
- Slight male and White population preponderance.
- Spontaneous involution or maturation occurs frequently; in situ neuroblastoma detected in 1 in 259 infant autopsies.
Etiology And Pathogenesis
Genetics And Chromosomal Abnormalities
- Etiology largely unknown.
- Familial cases represent 1-2%; associated with younger diagnostic age.
- Germline gain-of-function variants in ALK gene linked to familial neuroblastoma.
- Germline pathogenic variants in PHOX2B predispose to syndromic neuroblastoma.
- BARD1 gene identified as major genetic contributor.
- MYCN proto-oncogene amplification detected in 20% of primary tumors; strongly predicts advanced stage and poor prognosis.
- Segmental chromosomal aberrations (SCA) confer increased recurrence risk: loss of heterozygosity of 1p, 11q, 14q; gain of 17q,.
- Hyperdiploid tumor DNA content associated with favorable outcome in infants under 18 months without MYCN amplification.
- Diploid DNA content predicts less favorable outcome.
- Whole genome sequencing identifies additional loss of function in ATRX and TERT.
Associated Syndromes
| Syndrome Category | Specific Disorders |
|---|---|
| Neurocristopathy Syndromes | Hirschsprung disease, Congenital central hypoventilation syndrome (PHOX2B variant),. |
| Overgrowth Syndromes | Beckwith-Wiedemann syndrome, Hemihypertrophy. |
| RASopathies | Neurofibromatosis type I, Noonan syndrome, Costello syndrome. |
| Other Inherited Disorders | Turner syndrome, Fanconi anemia, Familial pheochromocytoma/paraganglioma, Li-Fraumeni syndrome,. |
| Environmental/Maternal | Fetal alcohol syndrome, fetal hydantoin syndrome. |
Pathology And Cellular Characteristics
- Extremely undifferentiated small round blue cell tumors to mature Schwannian stroma with ganglion cells.
- Characteristic histopathologic feature: Homer-Wright pseudorosettes (circular groupings of dark tumor cells surrounding pale neurofibrils).
Immunohistochemical Profile
| Marker Type | Findings |
|---|---|
| Positive Markers | Synaptophysin, tyrosine hydroxylase, PHOX2B, neuron-specific enolase (NSE), NB84. |
| Negative Markers | Hematopoietic markers (CD45), desmin, myogenin, keratin, CD99. |
Note: PHOX2B exhibits high specificity and sensitivity for neuroblastic tumors.
Clinical Manifestations
Anatomical Distribution And Local Symptoms
- Metastasizes via local invasion or distant hematogenous/lymphatic routes.
- Distant metastases present at diagnosis in 75% of cases.
| Primary Site | Frequency | Clinical Manifestations |
|---|---|---|
| Abdomen | 65% (46% Adrenal, 19% Paraspinal) | Asymptomatic palpable mass, abdominal distension, pain, renovascular hypertension. |
| Posterior Mediastinum | 25% | Dyspnea, dysphagia, pulmonary infections, lymphatic compression, stridor,. |
| Pelvis | 4% | Genitourinary obstruction, constipation. |
| Head And Neck | 3% | Palpable neck mass. |
Specific Clinical Syndromes
| Syndrome | Clinical Features And Pathophysiology |
|---|---|
| Horner Syndrome | Unilateral ptosis, miosis, anhidrosis; secondary to cervical or upper thoracic sympathetic compression. |
| Opsoclonus-Myoclonus-Ataxia (Dancing Eyes) | Myoclonic jerking, random conjugate eye movements, cerebellar ataxia; autoimmune paraneoplastic origin; often associated with biologically favorable tumors. |
| Kerner-Morrison Syndrome | Intractable secretory watery diarrhea and hypokalemia; caused by tumor secretion of vasoactive intestinal peptide (VIP). |
| Hutchinson Syndrome | Limping, irritability, bone pain; represents diffuse bone and bone marrow metastases. |
| Pepper Syndrome | Massive hepatomegaly with or without respiratory distress; characterizes Stage MS disease in infants. |
Diagnostic Evaluation
- Biochemical Markers: Elevated urinary catecholamine metabolites (homovanillic acid [HVA], vanillylmandelic acid [VMA]) detected in 95% of cases.
- Bone Marrow Evaluation: Bilateral aspirates and biopsies required. Diagnosis confirmed without primary tumor biopsy if marrow exhibits small round blue cells (rosettes) concurrently with elevated urinary catecholamines.
- Anatomical Imaging: Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) evaluates primary tumor extent. MRI strictly preferred for paraspinal lesions (assesses cord compression) and neck masses.
- Functional Imaging: 123I-MIBG (meta-iodobenzylguanidine) scintigraphy detects 90% of neuroblastomas; evaluates bone and soft tissue metastases. 18F-FDG PET utilized for MIBG-nonavid tumors.
Staging Systems
Historical use of International Neuroblastoma Staging System (INSS) replaced by image-based International Neuroblastoma Risk Group Staging System (INRGSS).
International Neuroblastoma Risk Group Staging System (INRGSS)
| Stage | Definition |
|---|---|
| L1 | Localized tumor confined to one body compartment; lacks Image-Defined Risk Factors (IDRFs). |
| L2 | Locoregional tumor demonstrating locally invasive features; presence of one or more IDRFs. |
| M | Distant metastatic disease (bone, bone marrow, liver, distant lymph nodes, other organs). |
| MS | Metastatic disease in children <18 months; metastases strictly confined to skin, liver, and/or bone marrow (<10% marrow involvement); lacks bone involvement. |
Prognostic Factors And Risk Stratification
Prognosis strongly dictated by clinical and biologic characteristics.
| Prognostic Factor | Favorable Profile | Unfavorable Profile |
|---|---|---|
| Age At Diagnosis | <18 months | $\ge$ 18 months. |
| Stage (INRGSS) | L1, L2, MS | M. |
| MYCN Status | Nonamplified | Amplified. |
| Tumor Ploidy (DNA Index) | Hyperdiploid (in infants) | Diploid. |
| Histology (INPC) | Differentiated; Low/Intermediate MKI | Undifferentiated; High MKI. |
| Chromosomal Aberrations | Absent | Present (LOH 1p, 11q; Gain 17q). |
Management And Therapeutics
Therapy risk-adapted incorporating age, stage, and molecular features.
Low-Risk Disease
- Encompasses Stage L1, select L2, and asymptomatic Stage MS.
- Primary Therapy: Surgical resection (L1/L2) or expectant observation (MS).
- Survival exceeds 90% without systemic therapy.
- Chemotherapy/Radiation reserved strictly for symptomatic life-threatening hepatomegaly (Pepper syndrome) in infants causing respiratory compromise.
Intermediate-Risk Disease
- Encompasses symptomatic <18 months L2, >18 months L2 with favorable biology, and infants (<12-18 months) with Stage M demonstrating favorable biology.
- Systemic Therapy: Moderate-dose multiagent chemotherapy. Regimen includes Carboplatin, Etoposide, Cyclophosphamide, and Doxorubicin.
- Therapeutic Goal: Achievement of partial response (>50% tumor volume reduction); complete resolution unnecessary.
- Surgery: Safe debulking post-chemotherapy; mutilating surgery avoided.
- Survival exceeds 90%.
High-Risk Disease
- Encompasses >18 months Stage M, any MYCN amplified tumor, and toddlers (12-18 months) Stage M with unfavorable biology.
- Phase 1: Induction Therapy
- Maximally reduce tumor burden.
- Dose-intensive multiagent chemotherapy: Topotecan, Cyclophosphamide, Cisplatin, Etoposide, Doxorubicin, Vincristine.
- Primary tumor surgical resection attempted post-induction.
- Phase 2: Consolidation Therapy
- Myeloablative chemotherapy followed by autologous peripheral blood stem cell (PBSC) rescue.
- Tandem (two sequential) autologous stem cell transplants yield superior event-free survival compared to single transplant.
- External beam radiotherapy to primary tumor bed and residual metastatic sites.
- Phase 3: Postconsolidation Therapy
- Targets minimal residual disease.
- Isotretinoin (13-cis-retinoic acid): Differentiating agent.
- Dinutuximab (ch14.18): Monoclonal antibody targeting GD2 disialoganglioside.
- GM-CSF: Co-administered with Dinutuximab.
- Long-term survival approximately 50% despite intensive multimodal intervention.
Oncologic Emergencies In Neuroblastoma
- Spinal Cord Compression: Invading paraspinal tumors cause neurologic deficits. Managed emergently with Dexamethasone and rapid initiation of chemotherapy. Surgical laminectomy reserved for chemotherapy failure (high risk of subsequent kyphoscoliosis),.
- Opsoclonus-Myoclonus-Ataxia Syndrome (OMAS): Managed via immune modulation (Corticosteroids, Intravenous Immunoglobulin, Rituximab). Neurologic sequelae frequently persist despite tumor eradication.