The first case was a 76-year-old man who was hospitalized with 11 years of bilateral lower extremity mobility limitation and 5 years of recurrent multiple fractures. In 2010, the patient began to suffer from fatigue of both legs after walking, inability to step on both legs, decreased height, hypophosphatemia, and other discomforts. Imaging in another hospital found local bone destruction in the upper segment of the right femur, and he underwent surgical resection of the lesion and right femoral head replacement. Postoperative pathological examination showed bone tissue degeneration, hyperemia, and a small amount of fibrosis. No other characteristic lesions were found. The patient's condition gradually worsened after operation, with decreased activity and multiple rib fractures. In 2016, octreotide imaging was performed in a hospital in Beijing, which suggested a right femoral lesion. Surgery was performed again, and postoperative pathological examination revealed a phosphaturic mesenchymal tumor in the right femur.
Postoperatively, the patient underwent outpatient reexamination, and the serum phosphorus was lower than before, so he was admitted to our hospital for treatment. The specific values of the patients' preoperative blood phosphorus, blood calcium, blood magnesium and other indicators are shown in Table 1. Physical examination revealed no obvious abnormality. In addition, PET-CT examination showed soft tissue nodules in front of the right femur, about 0.7 cm in diameter, with increased expression of somatostatin receptors: it is likely to be a phosphaturic mesenchymal tumor (Figure 1). Then, surgical resection was performed. The histology of the postoperative specimens showed that the tumor was composed of bland short spindle cells, smudgy/grungy basophilic matrix, mature adipose tissue, hemorrhage, and focal ossification (Figure 2). Immunohistochemical staining showed that vimentin, SATB2, CD56 and CD31 were positive, while CD34, SMA, desmin, CD99, Bcl-2, S-100, Syn, CK-pan and STAT6 were negative. The proliferation index Ki-67 was about 3% (Table 2). Compared with preoperative, the patient's serum phosphorus showed an overall upward trend, although it still did not return to normal half a year after the operation.