Other tumors of bone
Phosphaturic mesenchymal tumor

Author: Nat Pernick, M.D. (see Authors page)

Revised: 18 October 2016, last major update June 2005

Copyright: (c) 2003-2016,, Inc.

PubMed search: phosphaturic mesenchymal [title] tumor

Page views in 2017: 624
Page views in 2018 to date: 538
Cite this page: Phosphaturic mesenchymal tumor. website. Accessed December 18th, 2018.
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
Images hosted on PathOut server:

Giant cells

Case of the Week #63:

Various images

Positive stains
Differential diagnosis
Additional references