This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: CNS Tumors, Subject name: Pathology
[{'content': 'Which of the following is true about medulloblastoma? \nSelect and explain. \nA. Radiosensitive tumor, B. Hematogenous spread is common, C. Low proliferation index, D. Homer Wright rosettes are rarely seen', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The tumor occurs predominantly in children and exclusively in cerebellum (infratentorial tumor). Histopathological hallmark is Homer-Wright rosettes. Mitoses are abundant, and markers of cellular proliferation, such as Ki-67, are positive in a high percentage of the cells. Dissemination of tumor occurs through CSF giving rise to either extensive growth along the surface likened to "icing," or nodular "drop metastases," which tend to involve the cauda equina. It is a radiosensitive tumor. Radiotherapy improves the survival in children. Cranio-spinal irradiation (CSI) reduces the recurrence from CSF dissemination.', 'role': 'assistant'}]