A 2-year-old boy presents with a rapidly enlarging right-sided abdominal mass that does not cross the midline. He has fever and haematuria. Ultrasound shows an intrarenal solid mass with calcifications. Urinary VMA and HVA levels are normal. The MOST likely diagnosis and its embryological origin are:

• A Wilms tumour (nephroblastoma) arising from metanephric blastemal cells ✓
• B Neuroblastoma arising from neural crest cells of the adrenal medulla
• C Hepatoblastoma arising from hepatic progenitor cells; elevated AFP expected
• D Rhabdomyosarcoma of genitourinary origin

Explanation

Wilms tumour (nephroblastoma) is the most common primary renal tumour in children (peak age 3–4 years). It arises from malignant transformation of pluripotent metanephric blastemal cells that fail to differentiate normally. Key distinguishing features from neuroblastoma: intrarenal origin (does not cross midline in most cases), normal urinary catecholamines (VMA/HVA normal), and absence of calcifications (although calcifications can occur rarely). Neuroblastoma arises from neural crest-derived adrenal medulla or sympathetic ganglia, crosses the midline, and has elevated urinary catecholamines.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.