title: Tumor-Induced Osteomalacia: Increased Level of FGF-23 in a Patient with a Phosphaturic Mesenchymal Tumor at the Tibia Expressing Periostin.
abstract: In our case, a 45-year-old male patient had multiple fractures accompanied by hypophosphatemia. FGF-23 levels were significantly increased, and total body magnetic resonance imaging (MRI) revealed a tumor mass located at the distal tibia leading to the diagnosis of tumor-induced osteomalacia (TIO). After resection of the tumor, hypophosphatemia and the increased levels of FGF-23 normalized within a few days. Subsequent microscopic examination and immunohistochemical analysis revealed a phosphaturic mesenchymal tumor mixed connective tissue variant (PMTMCT) showing a positive expression of somatostatin receptor 2A (SSTR2A), CD68, and Periostin. Electron microscopy demonstrated a poorly differentiated mesenchymal tumor with a multifocal giant cell component and evidence of neurosecretory-granules. However, the resected margins showed no tumor-free tissue, and therefore a subsequent postoperative radiotherapy was performed. The patient is still in complete remission after 34 months. Tumor resection of PMTMCTs is the therapy of choice. Subsequent radiotherapy in case of incompletely resected tumors can be an important option to avoid recurrence or metastasis even though this occurs rarely. The prognostic value of expression of Periostin has to be evaluated more precisely in a larger series of patients with TIO.
authors.affiliation: Department of Internal Medicine III, Hematology/Internal Oncology, University Hospital of Regensburg, Franz-Josef-Strauß-Allee 11, 93053 Regensburg, Germany.
authors.forename: Anke H
authors.initials: AH
authors.lastname: Hautmann
authors.affiliation: Institute of Pathology, University Hospital of Regensburg, 93053 Regensburg, Germany.
authors.forename: Josef
authors.identifier: 0000-0002-4854-5881
authors.initials: J
authors.lastname: Schroeder
authors.affiliation: Institute of Surgical Pathology, University Hospital of Zurich, 8091 Zurich, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Wild
authors.affiliation: Department of Radiotherapy, University Hospital of Regensburg, 93053 Regensburg, Germany.
authors.forename: Matthias G
authors.initials: MG
authors.lastname: Hautmann
authors.affiliation: Institute of Pathology, University Hospital of Regensburg, 93053 Regensburg, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Huber
authors.affiliation: Institute of Radiology, Asklepios Clinic, 93077 Bad Abbach, Germany.
authors.forename: Patrick
authors.identifier: 0000-0001-7743-4163
authors.initials: P
authors.lastname: Hoffstetter
authors.affiliation: Department of Internal Medicine I, University Hospital of Regensburg, 93053 Regensburg, Germany ; Department of Rheumatology and Clinical Immunology, Asklepios Clinic, 93077 Bad Abbach, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Fleck
authors.affiliation: Department of General and Geriatric Medicine, Hospital of Barmherzige Brüder, 93049 Regensburg, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Girlich