What is the name of the malignant pediatric kidney tumor most commonly diagnosed in children five years of age or younger?

• A. Nephroblastoma
• B. Angiomyolipoma
• C. Rhabdomyosarcoma
• D. Oncocytoma

Answer: (A)

Wilms tumor, also called nephroblastoma, is the malignant pediatric kidney tumor most commonly diagnosed in children five years of age or younger. It arises from immature kidney tissue and typically presents as a unilateral abdominal mass, sometimes with hypertension or hematuria. Imaging often shows a large, well-defined intrarenal mass that distorts the kidney but remains confined to the organ in many cases; prognosis is favorable with appropriate treatment (surgery plus chemotherapy) for tumors with favorable histology. The other options are not the most common pediatric renal malignancies: angiomyolipoma is benign and more typical in adults or associated syndromes; rhabdomyosarcoma is a soft-tissue tumor that can involve the kidney area but is not the primary pediatric renal malignancy; oncocytoma is benign and usually seen in older adults.