This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Childhood Tumors, Subject name: Pediatrics
[{'content': "Most common tumor of kidney in children is: \nSelect and explain. \nA. Wilms' tumor, B. Neuroblastoma, C. Polycystic kidney disease, D. Renal cell carcinoma", 'role': 'user'}, {'content': "Answer: A \nExplanation: a. Wilms' tumor(Ref: Nelson's 20/e p 2464-2465)Wilms' tumor (WT), also known as nephroblastoma, is the most common primary malignant renal tumor of childhood;It is the second most common malignant abdominal tumor in childhood.The most common sites of metastases from Wilms tumor are the lungs, regional lymph nodes, and liver.", 'role': 'assistant'}]