Osteofibrous dysplasia

Osteofibrous dysplasia is a benign fibro-osseous cortical lesion that occurs almost exclusively occurs in the tibia and fibula. It is most commonly seen in the mid-diaphysis of the tibia. Some consider it synonymous with ossifying fibroma because of histological similarities, but it is generally considered a separate entity due to different presentation and treatment.

Terminology

A commonly used synonym is ossifying fibroma of the long bones.

Epidemiology

Most are seen around the age of

• most common in younger patients, e.g. ~ 10 years of age
  • less commonly reported in older patients, and there is likely a up to 63 years of age ³
• slight male predilection. (3:2 ratio ³)

Clinical presentation

Most patients present with pain and swelling, and patients may present secondary to a pathological fracture.

Pathology

Osteofibrous dysplasia is considered as a benign, non-neoplastic condition. Some consider it as part of a spectrum of osteofibrous dysplasia-like adamantinoma and adamantinoma.

Microscopic appearance

Histology shows trabecular bone woven within fibrous stroma with osteoblastic rimming and mature lamellar bone.

It is closely related to fibrous dysplasia (fibrous dysplasia is predominantly medullary), but the zonal phenomenon and osteoblastic rimming of bony trabeculae are absent in fibrous dysplasia.

Osteofibrous dysplasia and ossifying fibroma of the jaw have similar histological characteristics, but osteofibrous dysplasia shows cytokeratin-positive cells, whereas ossifying fibroma of the jaw shows psammomatous calcification, which are exclusive features.

Although adamantinoma can contain osteofibrous dysplasia-like components, nests or strands of an epithelioid cell are the differentiating feature between adamantinoma and osteofibrous dysplasia.

Adamantinoma with scarce epithelioid component and mostly composed of osteofibrous dysplasia-like tissue are considered as osteofibrous dysplasia-like adamantinoma.

Radiographic features

Osteofibrous dysplasia occursis classically a lytic lesion centered in the tibial cortex, often with sclerotic margins. Because of its similarity to adamantinoma, a younger age group than adamantinomamuch more aggressive pathology, which occursa primary issue is differentiating between the two.

Due to intralesional heterogeneity, needle biopsy may result in an older age groupdiagnostic misclassification, particularly with underestimation of aggressive lesions. They are usually Thus, radiologic-pathologic correlation is important with benign or equivocal biopsy results ³.

Osteofibrous dysplasia tends to be:

• smaller than adamantinomas - mean(mean 6-7 cm compared toversus 10-17 cm for adamantinoma.)
• with more distinct margins
• less likely to involve the medullary cavity

Plain radiograph

Plain radiograph remains the initial and chief investigation.

• location:
  • along the long axis: mid-diaphysis, especially anteriorly
  • location along the transverse axis: cortical with medullary encroachment
• consistency
  • lucent or ground-glass
  • lobular-to-bubbly in appearance
• lucent or ground-glass
margins
• narrow zone of transition
• well-defined sclerotic marginssclerosis common
• pseudotrabeculationsno nidus
• no aggressive periosteal reaction
  • benign-appearing periosteal reaction is non-specific, and can be seen in all lesions along the osteofibrous dysplasia/adamantinoma spectrum ³
• +/- pseudotrabeculation and anterior bowing may also be present
• no periosteal reaction and no nidus

MRI

MRI is usually the next stephelpful in investigatingevaluation of suspected osteofibrous dysplasia:, particularly to evaluate the extent of intramedullary involvement. Complete medullary cavity involvement is more suggestive of adamantinoma.

• T1: intermediate signal
• T2: intermediate-to-high signal
• T1C+: diffuse and intense enhancement.
• no+/- soft tissue component (non-specific)
  • can be seen in all lesions along the osteofibrous dysplasia/adamantinoma spectrum ³
• no aggressive cortical destruction

Treatment and prognosis

Surgery is reserved for lesions that are large or demonstrate aggressive behaviour.

They usually have an excellent prognosis and usually, stabilise or spontaneously regress once the child is over 10 years old.

It can be locally destructive and may result in pathological fracture, subsequently pseudarthrosis.

Local recurrences can occur after surgery with some aggressive recurrence, possibly due to components of adamantinoma or possible transformation to adamantinoma.

Differential diagnosis

• ossifying fibroma
• adamantinoma
• osteofibrous dysplasia-like adamantinoma
• intracortical fibrous dysplasia