Fibrous dysplasia

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Fibrous dysplasia
Diagnosis in short

Fibrous dysplasia. H&E stain.

Synonyms osteitis fibrosa

LM woven bone with odd irregular shapes (often described as "chinese characters"), fibrous tissue around bone, no osteoblastic rimming
LM DDx desmoplastic fibroma, low-grade fibrosarcoma, low-grade central osteosarcoma
Site bone

Syndromes McCune-Albright syndrome

Prevalence uncommon
Prognosis benign

Fibrous dysplasia, also osteitis fibrosa, is a rare disorder of bone that has a distinctive microscopic appearance.

General

Classification:

  • Monostotic - one bone involved, ~80% of cases.
  • Polyostotic - several bones involved, ~20% of cases.

Microscopic

Features:[1]

  • Woven bone with odd irregular shapes - key feature.
    • Described as "chinese characters".[2]
  • Fibrous tissue around bone.

Notes:

  • No osteoblastic rimming.

DDx:

  • Desmoplastic fibroma - has lamellar bone.
  • Low grade fibrosarcoma.
  • Low-grade central osteosarcoma.[3]
  • Gnathic ossifying fibroma (Cemento-ossifying fibroma)[4][5] - Prominent calcified spherules, no associated GNAS mutation
    • Gnathic ossifying fibroma recurs and needs to be completely enucleated
    • Fibrous dysplasia may be self limited and can be followed with observation or if symptomatic bisphosphonate therapy is an option.
    • S0, distinguishing between these two entities is important

Images

www:

Molecular

  • Postzygotic (somatic) activating mutations of the GNAS1 gene 10, which encodes the α-subunit of the stimulatory G-protein Gs[6]
  • Both mono and polyostatic cases.
  • Causative molecular lesion of McCune-Albright and Mazzabraud syndrome[7]

See also

References

  1. URL: http://www.pathologypics.com/pictview.aspx?id=104. Accessed on: 14 April 2011.
  2. URL: http://www.pathcases.com/bone_tumors_and_tumor.htm. Accessed on: 31 May 2011.
  3. Inwards, CY (2001). "Low-grade central osteosarcoma versus fibrous dysplasia". Pathology Case Reviews 6 (1): 22-27. http://journals.lww.com/pathologycasereviews/Fulltext/2001/01000/Low_Grade_Central_Osteosarcoma_Versus_Fibrous.5.aspx.
  4. http://www.nature.com/modpathol/journal/v20/n3/full/3800753a.html
  5. Patel, MM.; Wilkey, JF.; Abdelsayed, R.; D'Silva, NJ.; Malchoff, C.; Mallya, SM. (May 2010). "Analysis of GNAS mutations in cemento-ossifying fibromas and cemento-osseous dysplasias of the jaws.". Oral Surg Oral Med Oral Pathol Oral Radiol Endod 109 (5): 739-43. doi:10.1016/j.tripleo.2009.12.016. PMID 20346714.
  6. Weinstein, LS.; Shenker, A.; Gejman, PV.; Merino, MJ.; Friedman, E.; Spiegel, AM. (Dec 1991). "Activating mutations of the stimulatory G protein in the McCune-Albright syndrome.". N Engl J Med 325 (24): 1688-95. doi:10.1056/NEJM199112123252403. PMID 1944469.
  7. http://ghr.nlm.nih.gov/condition/mccune-albright-syndrome