A 2-year-old boy is brought to the emergency department with a 3-week history of progressive irritability, poor feeding, and constipation. His mother reports he has been 'not himself' and has developed a limp over the past week. On examination, he is pale and has a firm, non-tender mass in the left upper abdomen that does not cross the midline. Vital signs show hypertension (BP 110/70 mmHg). Laboratory investigations reveal hemoglobin 8.5 g/dL, elevated urinary catecholamine metabolites (VMA and HVA), and a normal renal function. Abdominal ultrasound shows a left suprarenal heterogeneous mass with areas of calcification. Which of the following is the most likely diagnosis and the most appropriate initial imaging for staging?

Explanation

## Clinical Diagnosis: Neuroblastoma **Key Point:** This is a classic presentation of neuroblastoma—a neural crest-derived malignancy arising from the adrenal medulla or sympathetic chain. The key diagnostic clues are: suprarenal location, elevated catecholamine metabolites (VMA/HVA), systemic symptoms (irritability, poor feeding), and hypertension from catecholamine excess. ### Differential Diagnosis: Wilms vs. Neuroblastoma | Feature | Wilms Tumor | Neuroblastoma | | --- | --- | --- | | **Origin** | Renal parenchyma | Adrenal medulla / sympathetic chain | | **Age at presentation** | 2–5 years (peak 3–4) | <5 years (peak <2 years) | | **Location** | Intrarenal, crosses midline | Suprarenal, does NOT cross midline | | **Hypertension** | Rare (<5%) | Common (50–60%) from catecholamine excess | | **Urinary catecholamines** | Normal | Elevated VMA, HVA | | **Calcification** | Rare | Common (50–80%) | | **Systemic symptoms** | Usually asymptomatic | Irritability, poor feeding, bone pain, paraneoplastic syndromes | | **Metastases** | Lungs, liver, contralateral kidney | Bones (femur, pelvis), bone marrow, liver, lungs | **High-Yield:** Elevated urinary VMA/HVA is pathognomonic for neuroblastoma and absent in Wilms tumor. This is a key discriminator. ### Staging Investigations for Neuroblastoma ```mermaid flowchart TD A[Confirmed Neuroblastoma]:::outcome --> B[MIBG Scintigraphy]:::action B --> C[Detects primary + bone metastases]:::outcome A --> D[CT Chest/Abdomen/Pelvis]:::action D --> E[Assesses local extent<br/>and visceral metastases]:::outcome A --> F[Bone Marrow Aspirate/Biopsy]:::action F --> G[Detects bone marrow involvement]:::outcome A --> H[MIBG or Bone Scan]:::action H --> I[Skeletal metastases]:::outcome ``` **Clinical Pearl:** MIBG (metaiodobenzylguanidine) scintigraphy is the gold standard for detecting neuroblastoma metastases, particularly bone and bone marrow involvement. It is more sensitive than bone scan for neuroblastoma-specific disease. ### Why This Is Neuroblastoma, Not Wilms Tumor 1. **Suprarenal location** (not intrarenal) → neuroblastoma arises from adrenal medulla 2. **Elevated urinary catecholamines (VMA/HVA)** → pathognomonic for neuroblastoma 3. **Hypertension** → from catecholamine excess (rare in Wilms) 4. **Calcification on imaging** → common in neuroblastoma, rare in Wilms 5. **Systemic symptoms** (irritability, poor feeding, bone pain) → paraneoplastic syndrome typical of neuroblastoma 6. **Age <2 years** → neuroblastoma peak incidence ### Why Not the Other Options? - **Wilms tumor:** The mass is suprarenal (not renal), and urinary catecholamines are normal in Wilms. Wilms does not cause hypertension or elevated VMA/HVA. - **Pheochromocytoma:** While it also causes hypertension and elevated catecholamines, pheochromocytoma is extremely rare in a 2-year-old and does not present with the systemic paraneoplastic features seen here. Neuroblastoma is the diagnosis in this age group. - **Hepatoblastoma:** The mass is clearly suprarenal on imaging, not hepatic. Hepatoblastoma does not cause elevated urinary catecholamines.