Soft tissue
Mesenchymal tumors
Phosphaturic mesenchymal tumor

Author: Vijay Shankar, M.D. (see Authors page)

Revised: 19 September 2016, last major update November 2012

Copyright: (c) 2002-2016,, Inc.

PubMed Search: Phosphaturic mesenchymal tumor

Cite this page: Phosphaturic mesenchymal tumor. website. Accessed March 28th, 2017.
Definition / General
  • Benign tumor of bone or soft tissue associated with rickets and osteomalacia (Am J Surg Pathol 1989;13:588)
  • Most cases of tumor associated oncogenic osteomalacia are due to phosphaturic mesenchymal tumor, which produces fibroblast growth factor-2, a protein that inhibits renal tubular phosphate reabsorption (Am J Surg Pathol 2004;28:1) or dentin matrix protein 1 (Mod Pathol 2004;17:573)
  • Extremely rare, median age 53 years, range 9 - 80 years, slight female predominance
  • Low serum phosphate, renal phosphate wasting, low 1,25-dihydroxy Vitamin D3
Case Reports
  • Complete excision causes dramatic reversal of signs and symptoms
Clinical Images

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Tumor of ethmoid sinus

Gross Description
  • 2 - 14 cm, arises in soft tissue and bone
Micro Description
  • Hypocellular tumor of bland spindle cells with small nuclei, indistinct nucleoli
  • Has hemangiopericytoma-like vasculature, osteoclast-like giant cells, distinctive "grungy" calcified matrix, fat, microcysts, hemorrhage, incomplete rim of membranous ossification, metaplastic bone
  • Infiltrative
  • No / rare mitotic activity, no atypia
  • Malignant cases: rare cases with nuclear atypia, 5+ mitotic figures / 10 HPF, high cellularity, resembles MFH
Micro Images

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Tumor of craniofacial sinuses

Tumor of ethmoid sinus

Mandible tumor

Positive Stains
  • Fibroblast growth factor-23, dentin matrix protein 1