phosphaturic mesenchymal tumor - orthopedic perspective

Background: Tumor-induced osteomalacia (TIO), also known as oncogenic osteomalacia, is a rare paraneoplastic disorder caused by secretion of fibroblast growth factor 23 (FGF23) by tumors. Phosphaturic mesenchymal tumors represent a rare etiology of TIO. These tumors are usually benign. Malignancy is noted in a minority of cases. The lesion may be located in the extremities and hence presented for a musculoskeletal oncology surgeon treatment. The unique biologic behaviour and natural history of these tumors are important determinants of the diagnostic and therapeutic rational.

Increased FGF23 levels causes renal phosphate wasting, hypophosphatemia, low 1,25-dihydroxy vitamin D levels, osteomalacia, and nonspecific symptoms including bone pain and musculoskeletal weakness. These symptoms usually accompany the patient for prolonged time periods before the elusive diagnosis of TIO, and the identification of the culprit lesion, are finally established. Therefore the surgical treatment is oftentimes delayed . The diagnosis of TIO is usually suspected when serum phosphate levels are chronically low in the setting of bone pain, fragility fractures and muscle weakness, resistant to vitamin D supplementation. Locating the offending tumor can be very difficult, as it is often very small and can be located anywhere in the body. Surgical removal of the tumor is the only definitive treatment.

In this essay we will review the unique entity of TIO due to Phosphaturic mesenchymal tumor, the diagnostic process required and the surgical treatment, through the cases treated at our institution.