Ossifying fibromas are benign bone lesions that should be differentiated from non-ossifying fibromas and fibrous dysplasia. Osteofibrous dysplasia is considered as a separate pathological entity in view of its different presentation and treatment, although histopathologically similar to ossifying fibroma. 

Epidemiology

These lesions are most frequently encountered in young children (often <10 years).

Associations

• hyperparathyroidism-jaw tumor syndrome

Pathology

Location

• lower extremity

  • tibia: most frequent site ⁵ (90% of the time); there is a predilection for the anterior tibial cortex

  • femur: occurs in a diaphysial location

• mandible and maxilla: these are examples of cementum-poor cemento-ossifying fibromas ² (see WHO classification scheme for odontogenic tumors)

• sinonasal: expansile lesions with peripheral ossification and central lucency

Microscopic appearance

They comprise haphazardly distributed lamellated bony spicules on a background of fibrous stroma. Despite being benign, they can be locally aggressive.

Immunophenotype

Immunohistochemical staining of lesions shows positive keratin cells in the majority of the cases.

Radiographic features

Plain radiograph / CT

• well-circumscribed lesion

• evidence of intracortical osteolysis with a characteristic sclerotic band (osteoblastic rimming)

• moderate cortical expansion

• homogeneous lesion matrix

MRI

Reported signal characteristics include:

• T1: low signal

• T2: iso-high signal; fluid-fluid levels may be present ⁸

• T1 C+ (Gd): typically shows enhancement

Treatment and prognosis

Ossifying fibromas tend to regress over time. For locally aggressive lesions, surgical resection is often curative although recurrence has been reported.

Complications

• pathological fracture

• limb bowing

Differential diagnosis

Imaging differential considerations include:

• fibrous dysplasia: has no osteoblastic rimming

• adamantinoma: may share a common origin with ossifying fibromas

• osteoid osteoma

• osteofibrous dysplasia