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': "A solid renal mass detected during prenatal ultrasound is most likely a \nSelect and explain. \nA. Wilm's tumor, B. Neuroblastoma, C. Clear cell sarcoma, D. Mesoblastic nephroma", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Mesoblastic nephroma is the most common solid renal tumor identified in the neonatal period and the most frequent benign renal tumor in childhood. It represents 3-10% of all pediatric renal tumors. Many cases are diagnosed with prenatal ultrasound and can manifest as polyhydramnios, hydrops, and premature delivery. Most of the patients are diagnosed before 3 mo of age, whereas WT is rarely diagnosed before 6 mo of age. Radical nephrectomy is the treatment of choice and may be sufficient by itself. Local recurrence is uncommon. Reference: Nelson; Neuroblastoma; Page no: 2467', 'role': 'assistant'}]