Osteofibrous dysplasia

==General== Rare, benign fibro-osseous lesion

• Alternate names
  • Congenital osteitis fibrosa

Template:Osteofibrous dysplasia
Diagnosis in short

• Location
  • Cortex of the tibial diaphysis

• Pathophysiology
  • May be either a clonal neoplastic lesion or a developmental dysplasia.
  • May be related to adamantinoma

• Presentation
  • Lower leg swelling
  • Pain
  • Tibial bowing

• Radiology
  • Intracortical lytic lesion
  • Surrounding zone of sclerosis
  • Seldom progresses radiologically

• Clinical DDX
  • Adamantinoma - usually older (teens-twenties), may have soft tissue extension
  • Metaphyseal fibrous defect - metaphyseal location
  • Fibrous dysplasia

• Prognosis
  • Self limited

• Population
  • Children
  • First 2 decades of life
  • Median 9.5 years

Microscopic

The lesion has a zonal architecture with a center of immature bone surrounded by more mature lamellar bone. The central spicules of woven bony trabeculae are lined by a layer of osteoblasts. The backgound is a loose and storiform fibrous tissue.

• Histologic DDX
  • Adamantinoma - epithelial elements are prominent and atypical
  • OFD-like adamantinoma (see below)
  • Fibrous dysplasia - Bony trabeculae lack osteoblastic rimming, not zonal

• Tips
  • Current discussion regarding the definition of an OFD-like adamantinoma.
    • WHO as of 2010 required absence of keratin-positive cells for OFD
    • Some accept as OFD lesions with scattered isolated keratin positive spindled cells.
    • Gray zone and varying interpretations of the boundry of OFD, OFD-like adamantinoma and adamantinoma.

• • The diagnosis depends on the ratio of fibrous to epithelial tissue which can vary within each particular tumor.
  • Therefore, ample tissue is required for accurate histologic diagnosis

IHC

Keratin positive isolated cells accepted by some.

Molecular

Clonal chromosomal abnormalities

• • Trisomies of chromosomes 7, 8, 12,21, and/or 22