This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Orthopedics, Subject name: Surgery
[{'content': 'A 25-year-old man presents with severe pain in the left femur. The pain is relieved by aspirin. On plain film, a 0.5-cm lucent lesion, which is surrounded by marked reactive sclerosis, is seen. select the type of bone lesion with which it is most likely to be associated (SELECT 1 LESION) \nSelect and explain. \nA. Osteoma, B. Osteoid osteoma, C. Osteoblastoma, D. Osteosarcoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Osteosarcoma, or osteogenic sarcoma, usually is seen in patients between the ages of 10 and 25 years. The distal femur is the site most frequently involved. The radiograph has a blastic, or sunburst, appearance. The tumor is not sensitive to radiation but does respond well to combination chemotherapy followed by surgical resection or amputation.An osteoid osteoma typically presents with severe pain that is characteristically relieved by aspirin. On radiograph, the lesion appears as a small lucency (usually <1.0 cm) within the bone that is surrounded by reactive sclerosis. These lesions gradually regress over 5-10 years, but most are excised to relieve symptoms. Surgical extirpation is usually curative.', 'role': 'assistant'}]