This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': "A patient with Ewing's sarcoma. Histology shows small round cells. These cells are filled with which of the following - \nSelect and explain. \nA. Glycogen, B. Iron, C. Fat, D. Mucin", 'role': 'user'}, {'content': "Answer: A \nExplanation: Ewing sarcoma \n\nIt is the second most bone sarcoma in children (after osteogenic sarcoma).\nIt is primary malignant small round cell tumor of bone.\nIt is derived from primitive neuroectoderm.\nAge → 10-15 years, Sex → M > F\nUsually arises in the diaphysis\n\nFemur & Tibia → 2/3rd\nFlat bones of pelvis\xa0→ 3/3rd\n\nImportant microscopic features\n\nScant cytoplasm in tumor cells which is clear because it is rich in glycogen.\nHomer - Wright rosettes.\n\nImportant Radiological features\n\nOnion-skin periosteal reaction.\nSun-rays appearance (more common in osteogenic sarcoma).\nCodman's triangle (It is also more common in osteogenic sarcoma).", 'role': 'assistant'}]