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': '13, years old boy, the LEAST common cause of proximal lytic lesion of the head of the femur is - \nSelect and explain. \nA. Plasmacytoma, B. Metastasis, C. Histiocytosis, D. Bone tumour', 'role': 'user'}, {'content': 'Answer: A \nExplanation: If multiple myeloma occurs as a solitary lesion it is known as Plasmacytoma\nAge gp is 6th-7th decade, Rare before 40yrs of age\nSo the lytic lesion in a 13 yrs old boy cannot be a plasmacytoma', 'role': 'assistant'}]