Phosphaturic mesenchymal tumor

Bone
Other tumors of bone
Phosphaturic mesenchymal tumor

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

Revised: 18 October 2016, last major update June 2005

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PubMed search: phosphaturic mesenchymal [title] tumor

Table of Contents

Cite this page: Phosphaturic mesenchymal tumor. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/bonephosphaturicmesenchymal.html. Accessed July 14th, 2017.

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

36 year old woman with muscle pain and weakness (Arch Pathol Lab Med 2002;126:1245)
53 year old man with a pretribial mass (Case of the Week #63)

Treatment

Complete excision causes dramatic reversal of signs and symptoms (Am J Surg Pathol 1989;13:588)

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

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