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': 'An 11year old boy presented with the complaints of pain in the right arm near the shoulder. X-ray examination revealed an expansile lytic lesion in the upper third of humerus. The most likely diagnosis is - \nSelect and explain. \nA. Giant cell tumor, B. Unicameral bone cyst, C. Osteochondroma, D. Parosteal osteosarcoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Two most important differential diagnosis of expansile lytic lesion in proximal humerus and proximal femur in children are : -\n\n\nSimple bone cyst (unicameral bone cyst)\nAneurysmal bone cyst\n\n\nAmong these two, only unicameral bone cyst is there in options. Therefore, no further discussion is required.', 'role': 'assistant'}]