Fibrous dysplasia

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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.

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] - 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

www:

See also

References