Bone & joints

Other tumors

Phosphaturic mesenchymal tumor

Topic Completed: 1 June 2005

Minor changes: 11 February 2021

Revised: 3 January 2019

Copyright: (c) 2003-2019,, Inc.

PubMed search: phosphaturic mesenchymal [title] tumor

Nat Pernick, M.D.
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Cite this page: Pernick N Phosphaturic mesenchymal tumor. website. Accessed October 25th, 2021.
Definition / general
  • Extremely rare
  • Median age 53 years, range 9 - 80 years, slight female predominance
  • Causes rickets or osteomalacia by producing a renal phosphaturic substance that reduces tubal phosphate reabsorption, causing low serum phosphate and resulting oncogenic osteomalacia; also low serum 1,25 dihydroxyvitamin D (Pediatr Dev Pathol 2000;3:61)
  • 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 epithelial phosphate transport, Am J Surg Pathol 2004;28:1) or dentin matrix protein 1 (Mod Pathol 2004;17:573)
  • Usually benign
Case reports
Gross description
  • 2 - 14 cm, arises in soft tissue and bone
Microscopic (histologic) description
  • Hypocellular tumor of bland spindled cells with small nuclei, indistinct nucleoli, osteoclast-like giant cells, myxoid change, hemangiopericytoma-like vessels, distinctive “grungy” calcified matrix, fat, microcysts, hemorrhage, incomplete rim of membranous ossification, metaplastic bone
  • Infiltrative
  • No / rare mitotic activity, no atypia
  • Malignant: rare cases with nuclear atypia, 5+ mitotic figures / 10 HPF, high cellularity, resembles MFH
Microscopic (histologic) images

Giant cells

Case of the Week #63:

Various images

Positive stains
Differential diagnosis
Additional references
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