1. OSTEOMALACIA DUE TO MESENCHYMAL TUMOR: SCINTIGRAPHIC DETECTION WITH OCTREOTIDE In-111 Panagiotis Heras (1), Theodosis Andrianopoulos (1), Ioannis Tsiverdis (1), Ilias Georgopoulos (1), Antonios Hatzopoulos (1) (1) Clinic of Internal Medicine, General Hospital of Nafplio, GREECE

2. Introduction: Oncogenic osteomalacia is a rare paraneoplastic syndrome, which is caused by tumors that secrete substances (FGF-23, sFRP-4, MEPE) leading to renal loss of phosphorus. The detection of the tumor is often difficult and raises a diagnostic challenge. Materials and Methods: A 55 year old male patient was diagnoses with osteomalacia on the basis of diffuse musculoskeletal pain, muscle weakness, elevated alkaline phosphatase, low serum concentration of phosphorus, phosphorus loss in urine, low levels of 1,25 (OH) 2vitaminiD3 and multiple incomplete fractures (Looser's zones). Despite the suspicion of paraneoplastic etiology of the osteomalacia and the extensive examination that included laboratory tests, CT scans and ultrasound, a related tumor was not revealed, therefore scintigraphy with octreotide labeled with Indium-111 (In-111) was conducted.

3. Results: Octreotide scintigraphy with In-111 (5 mCi), revealed an area of increased uptake, distal to the right knee. The radiological assessment with ultrasound, MRI and magnetic resonance angiography (MRA), confirmed the presence of small vascular soft-tissue mass in this area, close to the bifurcation of the right popliteal artery. The histological examination proved that there was a mesenchymal tumor, after the surgical removal of which, clinical and laboratory findings were fully restored and incomplete fractures were healed. Conclusion: Scintigraphy with octreotide labeled with Indium-111 is useful for detection of the mesenchymal tumors causing osteomalacia, since they usually express somatostatin receptors. The MRI and MRA facilitate surgical approach to these tumors.