This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bone Tumour, Subject name: Orthopaedics
[{'content': "An 8-year-male progressive swelling upper end tibia - irregular, local temperature raised, variable consistency and ill defined margins: \nSelect and explain. \nA. Giant cell tumor, B. Ewing's sarcoma, C. Osteogenic sarcoma, D. Secondary metastasis", 'role': 'user'}, {'content': "Answer: C \nExplanation: (c) Osteogenic sarcoma- The clinical presentation in question can occur both in Ewing's sarcoma and osteosarcoma.- History of trivial trauma- Progressive swelling- Raised local temperature- Variable consistency- Ill defined margins.- However, swelling is around the knee joint at upper end of tibia, which favors the diagnosis of osteosarcoma (metaphyseal lesion).- Ewing's sarcoma usually occurs in the diaphysis of the bone (middle of the shaft).", 'role': 'assistant'}]