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Open access

Maria P Yavropoulou, Christos Poulios, Christoforos Foroulis, Symeon Tournis, Prodromos Hytiroglou, Kalliopi Kotsa, Isaak Kessisoglou and Pantelis Zebekakis

Summary

Tumor-induced osteomalacia (TIO) is a rare form of hypophosphatemia usually caused by phosphaturic mesenchymal tumors (PMTs); the biologic behavior of PMTs is under investigation. Herein we present a case of TIO with a protracted course over 12 years leading to a fatal outcome. A 39-year-old man presented with weakness in 2004 and was found to have decreased serum phosphorus, phosphaturia and low levels of 1,25-dihydroxyvitamin D3. Four years later he developed a painful left calf mass. The lesion was resected, but recurred causing extreme pain and dysfunction. Radiological examination showed a large cluster of soft tissue tumors affecting all the muscle compartments of the calf and a smaller lesion inside the metaphysis of the tibia. Above-knee amputation was performed. Histological examination of all lesions showed a cellular spindle cell neoplasm with variously sized vessels, wide vessel-like spaces and scattered deposits of calcified extracellular material. The tumor infiltrated skeletal muscles, subcutaneous fat and the proximal end of the fibula. The tibial lesion had identical histology. Three years after the amputation the patient presented with cough and dyspnea. Radiological examination, followed by an open biopsy, showed that there were multiple metastatic nodules of PMTs in both lungs. Shortly after the diagnosis the patient died. This case illustrates that even benign cases of PMTs may lead to a fatal outcome and the classification of PMTs into benign and malignant should be reassessed in order to correspond to its biological behavior.

Learning points:

  • PMTs, aside from having locally aggressive behavior, may metastasize and cause death

  • PMTs may behave aggressively despite ‘benign’ histological findings

  • Accurate diagnosis of tumor-induced osteomalacia and patient management require a multidisciplinary approach

Open access

Hans-Christof Schober, Christian Kneitz, Franziska Fieber, Kathrin Hesse and Henry Schroeder

Summary

Tumor-induced osteomalacia (TIO) is caused by the hormone fibroblast growth factor 23 (FGF-23). It is mainly produced in the tissue of mesenchymal tumors. Patients with TIO frequently suffer from a chronic decompensated pain syndrome and/or muscle weakness with postural deformity. Despite the severity of the disease, the diagnosis is frequently established late. In some cases, it takes several years to establish the condition. This case report concerning a 68-year old woman demonstrates the selective blood sampling for FGF-23 as path-breaking diagnostics to confirm the diagnosis of a neuroendocrine tumor.

Learning points:

  • Tumor-induced osteomalacia is a rare condition compared to other paraneoplastic syndromes.

  • It causes complex symptoms such as progressive reduction of physical capacity, exhaustion, fatigue, a decompensated pain syndrome of the musculoskeletal system and fractures of several bones.

  • Elevated serum levels of FGF-23 implicate massive phosphate elimination and resulting hypophosphatemia.

  • The diagnosis is often established over a period of several years because the localization of small FGF-23-producing tumors is complicated.

  • It is the combination of MRI and selective blood sampling for FGF-23 which permits reliable identification of tumors causing TIO and leads to accurate localization.

  • In a patient with generalized pain and reduced physical capacity, osteological parameters such as phosphate, 25-OH vitamin D3 and 1,25-(OH)2D3, as well as bone-specific alkaline phosphatase levels in serum should be determined. Hypophosphatemia should always lead to further diagnostic investigations aiming at the detection of an FGF-23-producing tumor.

Open access

Shintaro Kawai, Hiroyuki Ariyasu, Yasushi Furukawa, Reika Yamamoto, Shinsuke Uraki, Ken Takeshima, Kenji Warigaya, Yuji Nakamoto and Takashi Akamizu

Summary

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome characterized by renal phosphate wasting leading to hypophosphatemia due to excessive actions of fibroblast growth factor 23 (FGF23) produced by the tumors. Although the best way of curing TIO is complete resection, it is usually difficult to detect the culprit tumors by general radiological modalities owing to the size and location of the tumors. We report a case of TIO in which the identification of the tumor by conventional imaging studies was difficult. Nonetheless, a diagnosis was made possible by effective use of multiple modalities. We initially suspected that the tumor existed in the right dorsal aspect of the scapula by 68Ga-DOTATOC positron emission tomography/computed tomography (68Ga-DOTATOC-PET/CT) and supported the result by systemic venous sampling (SVS). The tumor could also be visualized by 3T-magnetic resonance imaging (MRI), although it was not detected by 1.5T-MRI, and eventually be resected completely. In cases of TIO, a stepwise approach of 68Ga-DOTATOC-PET/CT, SVS and 3T-MRI can be effective for confirmation of diagnosis.

Learning points:

  • TIO shows impaired bone metabolism due to excessive actions of FGF23 produced by the tumor. The causative tumors are seldom detected by physical examinations and conventional radiological modalities.

  • In TIO cases, in which the localization of the culprit tumors is difficult, 68Ga-DOTATOC-PET/CT should be performed as a screening of localization and thereafter SVS should be conducted to support the result of the somatostatin receptor (SSTR) imaging leading to increased diagnosability.

  • When the culprit tumors cannot be visualized by conventional imaging studies, using high-field MRI at 3T and comparing it to the opposite side are useful after the tumor site was determined.

Open access

Maria P Yavropoulou, Nikolina Gerothanasi, Athanasios Frydas, Evangelia Triantafyllou, Chris Poulios, Prodromos Hytiroglou, Panagiotis Apostolou, Ioannis Papasotiriou, Symeon Tournis, Isaak Kesisoglou and John G Yovos

Summary

Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome caused primarily by benign mesenchymal tumors. These tumors typically follow a benign clinical course and local recurrence occurs in <5% of cases. We investigated a 49-year-old man with a recurrent mesenchymal phosphaturic tumor showing no signs of malignancy. The patient suffered from chronic muscle weakness, myalgia and cramps. His medical record included the diagnosis of oncogenic osteomalacia, for which he was submitted to tumor resection in the left leg three times before. Laboratory examination showed hypophosphatemia, hyperphosphaturia and an elevated serum FGF23 level. A radical surgical approach (amputation) was advised, however, complete biochemical and clinical remission was not reached. Molecular analysis of the tumor cells demonstrated overexpression of growth factor receptors implicated in tumor angiogenesis and metastatic potential (platelet derived growth factor type A (PDGFRA), PDGFRB and vascular endothelial growth factor receptor) together with increased expression of FGF23, x-linked-phosphate-regulating endopeptidase and KLOTHO. TIO is usually associated with benign phosphauturic tumors and, when identified, resection of the tumor leads to complete remission in the majority of cases. The underlying pathophysiology of recurrences in these tumors is not known. This is the first report showing increased expression of growth factor receptors in a locally aggressive but histopathologically benign phosphaturic mesenchymal tumor.

Learning points

  • TIO is usually associated with benign soft tissue or bone neoplasms of mesenchymal origin.

  • These tumors typically follow a benign clinical course and even in the rare malignant cases local recurrence occurs in <5%.

  • Successful identification and removal of the tumor leads to full recovery in the majority of cases.