Soft tissue

Uncertain differentiation

Phosphaturic mesenchymal tumor

Last author update: 1 November 2012
Last staff update: 4 June 2021

Copyright: 2002-2022,, Inc.

PubMed Search: Phosphaturic mesenchymal tumor

Vijay Shankar, M.D.
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Cite this page: Shankar V. Phosphaturic mesenchymal tumor. website. Accessed August 11th, 2022.
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-23, 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
Microscopic (histologic) 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
Microscopic (histologic) 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
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