This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bone Tumour, Subject name: Orthopaedics
Most common malignant tumour of bone is: 
Select and explain. 
A. Osteogenic sarcoma, B. Chondro sarcoma, C. Ewing's sarcoma, D. Metastasis
D: Metastasis
Answer: D: Metastasis 
Explanation: (Metastatic bone disease) (224-M) (193-Apley's 8th)Metastatic bone disease - In patients over 50 years bone metastasis are seen more frequently than all primary malignant bone tumours.* Commonest source is carcinoma of breast, next in frequency are prostate, kidney, lung, thyroid, bladder and GIT* Commonest sites for bone metastasis are -vertebrae pelvis the proximal half of the femur and the humerus* Spread is usually via the blood stream.