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: Orthopaedics
[{'content': 'True about parosteal osteosarcoma - \nSelect and explain. \nA. Same prognosis as medullary type, B. Never go to medulla, C. May involve medulla, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: This question is quite different from previous one.\nThough medullary cavity is not involved in parosteal osteosarcoma, some dedifferentiated type (grao sarcoma may involve medullary cavity. -- DD of bone tumor.', 'role': 'assistant'}]