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 68-year-old man comes to the physician because of a 5-month history of undulating, dull pain in his right thigh. Physical examination shows a tender, round mass located above the right knee on the anterior aspect of the thigh. An x-ray of the right thigh shows sunburst pattern of osteolytic bone lesions in combination with sclerotic bone formation and invasion of the surrounding tissue. Despite limb-sparing attempts, the patient has to undergo amputation of the right leg. A photograph of a cross-section of the affected leg is shown. Which of the following is the strongest predisposing factor for this patient's condition?
assistant
Paget disease of bone