Oncogenic osteomalacia: localization of underlying peripheral mesenchymal tumors with use of Tc 99m sestamibi scintigraphy.

Objective: To highlight a strategy for potential detection of mesenchymal tumors in oncogenic malacia, as illustrated by 3 cases.

Methods: Three case reports are presented in which successful localization of the offending neoplasm was accomplished by using whole-body Tc 99m sestamibi scanning. Alternative localization techniques are also reviewed.

Results: Oncogenic osteomalacia occurs infrequently and is caused by neoplasms that secrete phosphatonins, substances that interfere with proximal tubular resorption of phosphorus and can result in phosphaturia, hypophosphatemia, reduced 1,25-dihydroxyvitamin D concentration, and osteomalacia. Removal of the underlying neoplasm results in complete resolution of all biochemical, pathologic, and physical manifestations of this disorder, as shown in our 3 patients. Because the neoplasms are small and can occur in any tissue compartment, they are difficult to localize, a feature that often results in therapeutic failure.

Conclusion: We conclude that use of whole-body Tc 99m sestamibi scanning may be an appropriate and cost-effective initial strategy for the localization of peripheral phosphatonin-secreting tumors.