Localisation of mesenchymal tumours by somatostatin receptor imaging

Oncogenic osteomalacia, an acquired hypophosphataemic syndrome associated with mesenchymal tumours, is characterised by hypophosphataemia secondary to inappropriate phosphaturia, reduced concentrations of serum calcitriol, and defective bone mineralisation. Removal of these tumours results in complete reversal of these biochemical defects. However, because these tumours are small, slow-growing, and frequently situated in unusual anatomical sites, conventional imaging techniques often fail to detect them. Since mesenchymal tumours express somatostatin receptors, we postulated that somatostatin analogues would be able to detect these tumours. We did Indium-111 labeled pentetreotide imaging in seven patients with oncogenic osteomalacia. In five patients, we identified a mesenchymal tumour, and clinical improvement occurred after tumour resection. Our findings suggest that 111In-pentetreotide imaging effectively detects occult mesenchymal tumours and facilitates surgical treatment of oncogenic osteomalacia.