This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ohopedics Oncology, Subject name: Orthopaedics
[{'content': "Matrix forming tumor is: \nSelect and explain. \nA. Osteosarcoma, B. Chondrosarcoma, C. Fibrosarcoma, D. Ewing's sarcoma", 'role': 'user'}, {'content': "Answer: A \nExplanation: OSTEOSARCOMA-MATRIX FORMING TUMOR CAUSE OF CALCIFICATION Osteosarcoma is a cancer of young (10-20 years). M/E - malignant cells with osteoid formation. Osteosarcoma is the most common radiation induced sarcoma Most commonly involves femur( lower end) and shows Codman's triangle or sunray appearance of periosteal reactions. Osteosarcoma- most common metastasis is to lung.", 'role': 'assistant'}]