This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urinary tract, Subject name: Anatomy
Most impoant prognostic factor of Wilms tumor 
Select and explain. 
A. Histopathology and ploidy of cells, B. Tumor stage, C. Age of patient, D. Mutation of chromosome 1p
B: Tumor stage
Answer: B: Tumor stage 
Explanation: histology remains a critical determinant of adverse prognosis. Even anaplasia restricted to the kidney (i.e., without extra-renal spread) confers an increased risk of recurrence and death, emphasizing the need for accurate identification of this histologic feature. Molecular parameters that correlate with adverse prognosis include loss of genetic material on chromosomes 11q and 16q, and gain of chromosome 1q inthe tumor cells. Along with the increased survival of individuals with Wilms tumor have come repos of an increased risk of developing second primary tumors, including bone and soft-tissue sarcomas, leukemia