system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A metastatic tumour least common in -
assistant
The correct answer is  The commonest sites for bone metastases are the vertebrae (commonest), pelvis, the proximal half of the femur, the humerus and ribs.
Extremities distal to elbow and knee are least commonly involved sites.