Which of the following has the potential of undergoing `Spontaneous' malignant transformation?

Complications of the Paget's disease include stress fractures and secondary sarcomas.  Poor mechanical properties of pagetic bone results in incomplete stress fractures. Fractures occur most commonly in the femur followed by other stress-bearing bones such as tibia, humerus, spine, and pelvis. Osteosarcomas and to a lesser extent, chondrosarcomas and fibrosarcomas are the most serious complications of Paget's disease. Prognosis of polyostotic Paget's disease is less favourable than monostotic disease. Patients with polyostotic disease are at higher risk of complications. Reference: Shafer’s Textbook of ORAL PATHOLOGY Eighth Edition page no 471,473