Which single clinical feature best distinguishes neuroblastoma from Wilms tumor in a 3-year-old child presenting with an abdominal mass?

Explanation

## Distinguishing Neuroblastoma from Wilms Tumor ### Key Biochemical Marker **Key Point:** Elevated urinary catecholamine metabolites (vanillylmandelic acid [VMA] and homovanillic acid [HVA]) are pathognomonic for neuroblastoma and are present in ~90% of cases. This is the single most discriminating biochemical feature. ### Comparative Feature Table | Feature | Neuroblastoma | Wilms Tumor | |---------|---------------|-------------| | **Catecholamine metabolites** | ↑ VMA/HVA in 90% | Normal | | **Associated syndromes** | Beckwith-Wiedemann, hemihypertrophy | WAGR, aniridia, Denys-Drash | | **Hematuria** | Rare | Common (40–50%) | | **Age of onset** | <5 years (median 2–3 yr) | <5 years (median 3–4 yr) | | **Primary site** | Adrenal medulla, sympathetic chain | Renal parenchyma | | **Metastases at diagnosis** | 50–60% | 10–15% | ### Clinical Pearl **Clinical Pearl:** VMA and HVA measurement is standard in the diagnostic workup of any child with a suspected neural crest tumor. A positive result strongly favors neuroblastoma and should prompt imaging of the sympathetic chain (chest, abdomen, pelvis). ### High-Yield Distinction **High-Yield:** While both tumors present with abdominal mass in young children, neuroblastoma arises from neural crest–derived sympathetic tissue and produces catecholamines; Wilms tumor arises from embryonic renal tissue and does not produce these metabolites. This biochemical difference is the most reliable discriminator. [cite:Robbins 10e Ch 10]