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': 'A 10-year child presented with a mid tibial swelling which an x-ray revealed a lytic lesion with sclerotic margins. What is the most likely diagnosis? \nSelect and explain. \nA. Eosinophilic granuloma, B. Osteoid osteoma, C. Fibrocortical defect, D. Fibrous dysplasia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: An osteoid osteoma is a benign bone tumour that arises from osteoblasts and was originally thought to be a smaller version of an osteoblastoma.\nOsteoid osteomas tend to be less than 1.5 cm in size.\nA tumour can be in any bone in the body but are most common in long bones, such as the femur and tibia.', 'role': 'assistant'}]