Soft tissue

Uncertain differentiation

Phosphaturic mesenchymal tumor

Last author update: 1 November 2012
Last staff update: 11 January 2023

Copyright: 2002-2023,, Inc.

PubMed Search: Phosphaturic mesenchymal tumor

Vijay Shankar, M.D.
Nat Pernick, M.D.
Page views in 2022: 3,197
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Cite this page: Shankar V. Phosphaturic mesenchymal tumor. website. Accessed November 29th, 2023.
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 or dentin matrix protein 1, causing low serum phosphate and resulting oncogenic osteomalacia; also low serum 1,25 dihydroxyvitamin D (Am J Surg Pathol 2004;28:1, Mod Pathol 2004;17:573, Pediatr Dev Pathol 2000;3:61)
  • 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
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

Contributed by Sharon Bihlmeyer, M.D. (Case #63) and AFIP

Various images

Giant cells

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Tumor of craniofacial sinuses

Tumor of ethmoid sinus

Mandible tumor

Positive stains
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