Fibrous dysplasia

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

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

General

Classification:

• Monostotic - one bone involved, ~80% of cases.
• Polyostotic - several bones involved, ~20% of cases.
  • May be associated with McCune-Albright syndrome.

Microscopic

Features:

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

Notes:

• No osteoblastic rimming.

DDx:

• Desmoplastic fibroma - has lamellar bone.
• Low grade fibrosarcoma.
• Low-grade central osteosarcoma.
• Gnathic ossifying fibroma (Cemento-ossifying fibroma)<ref>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.<r/ref> - 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.
  • Distinguishing between these two is important

Images

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  Fibrous dysplasia - low mag. (WC/Nephron)

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  Fibrous dysplasia - intermed. mag. (WC/Nephron)

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  Fibrous dysplasia - high mag. (WC/Nephron)

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  Medium power shot with the classic 'Chinese character' bone spicules.

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  Immature bony trabeculae in a fibrous stroma.

www:

• Fibrous dysplasia of bone - high mag. (pathologypics.com).
• Fibrous dysplasia of bone - low mag. (pathologypics.com).
• Modern Pathology[1]

See also

• Bone.