A 50-year-old woman comes to the physician for gradually increasing back pain for the past 3 weeks. She has no history of trauma. She is a non-smoker. Blood and urine findings are normal. X-ray of the spine shows two lytic lesions at T11 and L2. Which of the following is the most likely diagnosis?
Avascular necrosis
Breast cancer
Osteoporosis
Osteosarcoma
Renal osteodystrophy
