Missed causative tumors in diagnosing tumor - 1 8 induced osteomalacia with F - FDG PET / CT : a potent

Objective: We describe herein two tumor-induced osteomalacia (TIO) cases for whom the causative lesions, located in their popliteal fossa, that were not identi ed in the standard eld of uorine-1818 uorodeoxyglucose positron emission tomography/computed tomography ( F-FDG PET/CT), which usually images only the head, trunk, and proximal parts of the extremities. Clinical Presentation and Intervention: A 47 years old Japanese man with multiple pathological fractures due to osteomalacia, accompanied by muscle weakness, hypophosphatemia, and an elevation of alkaline phosphatase (ALP) 18 18 was referred to our hospital. A F-FDG PET/CT scan was performed, but no F-FDG uptake was detected in the standard eld of imaging. Magnetic resonance imaging revealed a small subcutaneous tumor (1.9×1.2×0.6cm) of the left posteriomedial knee, displaying uniform enhancement on gadoliniumenhanced T1-weighted fat-suppression imaging. The tumor was resected widely and diagnosed as phosphaturic mesenchymal tumor, mixed connective tissue variant (PMTMCT). The other patient was a 31 years old Japanese woman with multiple pathological fractures, hypophosphatemia and elevated of ALP and was referred to our hospital on suspicion of TIO. Although the causative lesion was not identi ed in 18 18 the standard eld of F-FDG PET/CT, F-FDG uptake (SUVmax 2.9) was detected on the right knee in the 18 additional whole-body F-FDG PET/CT. Magnetic resonance imaging revealed a soft-tissue tumor (6.4×4.1×2.9cm) in the right posterior knee. Following biopsy, the tumor was marginally resected, and was pathologically diagnosed as PMTMCT. Conclusion: Once patients are suspected to have TIO, a whole18 body nuclear imaging study such as F-FDG PET/CT should be performed, in order not to miss the hidden causative tumor, especially occurring in the distal extremities. Hell J Nucl Med 2016; 19(1): 46-48 Epub ahead of print: 1 March 2016 Published online: 1 April 2016