A 74-year-old man with known Paget's disease of bone develops worsening thigh pain. Serum alkaline phosphatase, previously elevated at 400 IU/L, has recently risen to 1800 IU/L. Radiograph shows destruction of the previous pagetic pattern with cortical breakthrough and a soft tissue mass. The most likely diagnosis is:
- A Hypercalcemia from accelerated pagetic turnover
- B Pathological fracture through Paget's bone
- C Pagetic sarcoma (osteosarcoma arising in Paget's bone) ✓
- D Giant cell tumor complicating Paget's disease
Explanation
Sarcomatous degeneration is the most feared complication of Paget's disease, occurring in approximately 1% of patients with polyostotic involvement. It typically manifests as a sudden rise in serum alkaline phosphatase (ALP) in a previously stable patient, new or worsening pain, cortical destruction, and a soft tissue mass on imaging. Histologically, most are osteosarcomas or fibrosarcomas. The prognosis is extremely poor (5-year survival <5%) because these tumors are usually high-grade at diagnosis and occur in elderly patients with limited surgical options. Giant cell tumors do complicate Paget's but are less common.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.