Osteofibrous dysplasia

Osteofibrous dysplasia is a benign fibro-osseous cortical lesion, that 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 10 years, and there is likely a slight male predilection.

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 benign 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 dyplasia is predominantly medullary), but 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 and, 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 epithelioid cell isare the differentiating feature between adamantioma 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 occuroccurs in a younger age group than adamantinoma, which occuroccurs in an older age group. They are usually smaller than adamantinomas - mean 6-7 cm compared to 10-17 cm for adamantinoma.

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
• lobular-to-bubbly in appearance
• lucent or ground-glass
• narrow zone of transition
• well-defined and sclerotic margins
• pseudotrabeculations and anterior bowing may also be present
• no periosteal reaction and no nidus

MRI

MRI is usually the next step in investigating suspected osteofibrous dysplasia:

• T1: intermediate signal
• T2: intermediate-to-high signal
• T1C+: diffuse and intense enhancement.
• no soft-tissue component
• no 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 older thanover 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