Paget's sarcoma of bone.

The most sinister complication of Paget's disease is malignant degeneration. The true etiology of Paget's disease remains unproven and unknown. The relative incidence of sarcoma ranges from 0.9% to 20% depending upon the population source. The anatomical distribution of lesions is similar to that of uncomplicated Paget's disease except for the high incidence in the humerus and rare occurrence in the spine. Approximately 50% of the lesions histologically represent osteosarcomas, with fibrosarcoma, fibrous histiocytoma, chondrosarcoma and giant cell tumor rarely occurring. The radiographic presentation is most commonly lytic, but sclerotic and mixed patterns occur. Cortical destruction and soft tissue mass are the cardinal radiographic signs. Malignant periosteal response is seldom found associated with Paget's sarcoma. The most common sites are femur, humerus, pelvis, skull and tibia. The prognosis is fatal at a very rapid rate. There are but a few isolated cases of long-term survival reported.