A 3-year-old girl from Delhi presents with her father with a 3-week history of irritability, poor appetite, and low-grade fever. On examination, she has a firm, non-tender mass in the left upper abdomen extending across the midline. The mass is fixed and does not move with respiration. Vital signs show mild hypertension (BP 110/70 mmHg). Laboratory investigations reveal elevated 24-hour urine catecholamines (3.5 times normal) and elevated serum LDH (1200 IU/L). Abdominal CT shows a 6 cm heterogeneous mass in the left adrenal gland with calcification and areas of necrosis. What is the most likely diagnosis?

Explanation

## Clinical Diagnosis: Neuroblastoma ### Key Clinical Features **Key Point:** Neuroblastoma is the most common extracranial solid malignancy in children, arising from neural crest cells of the sympathetic nervous system. It presents with constitutional symptoms, elevated catecholamine metabolites, and an adrenal/paravertebral mass. This case demonstrates the classic presentation: 1. **Age:** 3 years (peak incidence < 5 years) 2. **Constitutional symptoms:** Irritability, poor appetite, fever (paraneoplastic) 3. **Mass location:** Left adrenal gland (primary site in 40% of cases) 4. **Biochemical marker:** Elevated 24-hour urine catecholamines (VMA, HVA) 5. **Imaging:** Adrenal mass with calcification and necrosis 6. **Hypertension:** Due to catecholamine excess ### Differential: Wilms Tumor vs. Neuroblastoma | Feature | Wilms Tumor | Neuroblastoma | |---------|-------------|---------------| | **Origin** | Renal parenchyma | Adrenal gland / sympathetic chain | | **Age** | 2–5 years | < 5 years (often < 2) | | **Mass location** | Intrarenal | Extrarenal (adrenal/paravertebral) | | **Hematuria** | Rare (< 10%) | Absent | | **Hypertension** | Rare | Common (25–30%) | | **Catecholamine elevation** | Absent | Present (VMA, HVA) | | **Calcification** | 5–10% | 50–80% | | **Associated syndromes** | WAGR, Denys-Drash, BWS | NF-1, familial neuroblastoma | **High-Yield:** Elevated 24-hour urine catecholamines are diagnostic for neuroblastoma and virtually absent in Wilms tumor. ### Pathophysiology Neuroblastoma arises from **neural crest-derived sympathoblasts** of the adrenal medulla or sympathetic chain. The tumor can undergo **spontaneous differentiation** to ganglioneuroblastoma or ganglioneuroma, or **spontaneous regression** (especially in infants < 1 year). **Mnemonic:** SIADH in Neuroblastoma = **S**ympathetic tumor → **I**ncreased catecholamines → **A**drenergic effects + **D**ifferentiation potential → **H**ypertension ### Diagnostic Markers 1. **Catecholamine metabolites (most sensitive):** - 24-hour urine **VMA** (vanillylmandelic acid) - 24-hour urine **HVA** (homovanillic acid) - Elevated in ~90% of cases 2. **Serum markers:** - **NSE** (neuron-specific enolase) — elevated in 50–75% - **LDH** — elevated (prognostic: high LDH = poor prognosis) - **Ferritin** — elevated (prognostic marker) 3. **Imaging:** - Abdominal ultrasound (first-line) - CT/MRI for local staging - **MIBG scan** (meta-iodobenzylguanidine) — specific for sympathetic tissue, detects primary and metastatic disease - Bone marrow biopsy (for metastatic staging) **Clinical Pearl:** MIBG scan is the gold standard for detecting metastatic neuroblastoma; it localizes to catecholamine-producing cells. ### INSS Staging (International Neuroblastoma Staging System) | Stage | Description | |-------|-------------| | 1 | Localized tumor, complete gross excision | | 2A | Localized tumor, incomplete excision | | 2B | Localized tumor with regional lymph node involvement | | 3 | Unresectable tumor or crossing midline | | 4 | Distant metastases (bone, bone marrow, liver, distant lymph nodes) | | 4S | Localized tumor with metastases limited to liver, skin, bone marrow (< 10%) — infants only | **High-Yield:** Stage 4S (special infant stage) can undergo spontaneous regression; prognosis is better than stage 4 in older children. ### Prognostic Factors **Favorable:** - Age < 18 months - Stage 1, 2, or 4S - Diploid DNA - Low MYCN copy number - Differentiated/ganglioneuroblastoma histology **Unfavorable:** - Age > 18 months - Stage 3 or 4 - MYCN amplification (2-fold increase in mortality) - Hyperdiploid DNA - Undifferentiated histology ### Management ```mermaid flowchart TD A[Neuroblastoma diagnosed]:::outcome --> B{Stage and risk?}:::decision B -->|Low/intermediate risk| C[Surgery ± chemotherapy]:::action B -->|High risk| D[Intensive chemotherapy]:::action D --> E[Surgery after chemotherapy]:::action E --> F[Radiation therapy]:::action F --> G[Autologous stem cell transplant]:::action G --> H[Isotretinoin maintenance]:::action H --> I[Long-term follow-up]:::outcome ``` **Clinical Pearl:** High-risk neuroblastoma (MYCN-amplified, stage 4 in children > 18 months) requires intensive multimodal therapy including chemotherapy, surgery, radiation, and autologous stem cell transplantation.