This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metastatic Bone Disease, Subject name: Orthopaedics
13, years old boy, LEAST common cause of proximal lytic lesion of head of femur is: 
Select and explain. 
A. Plasmacytoma, B. Metastasis, C. Histiocytosis, D. Bone tumour
A: Plasmacytoma
Answer: A: Plasmacytoma 
Explanation: Ans. is 'a' Plasmacytoma If multiple myeloma occurs as a solitary lesion it is K/a PlasmacytomaAge gp is 6th-7th decade, Rare before 40yrs of ageSo the lytic lesion in a 13yrs old boy cannot be a plasmacytoma