A 60-year-old woman reported difficulty walking, with pain in the back, ribs, left shoulder, and pelvis. A bone scan performed because of acute exacerbation of pain in the sacral area showed multiple insufficiency fractures. Treatment for hypophosphatemic osteomalacia was unsuccessful and the patient continued to have pathologic fractures. A Tc-99m sestamibi scan was performed and identified a potential oncogenic source. The mass was removed with wide borders and found to be a low-grade mesenchymal tumor. Within months after surgery, the patient improved dramatically and is walking without assistance.