Ossifying fibroma
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.
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Epidemiology
These lesions are most frequently encountered in young children (often <10 years).
Pathology
Histology
They comprise haphazardly distributed lamellated bony spicules on a background of fibrous stroma. Despite being benign, they can be locally aggressive. Immunohistochemical staining of lesions shows positive keratin cells in the majority of the cases.
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
Associations
Radiographic features
Plain radiograph and 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
- T1 C+ (Gd): typically shows enhancement
Treatment and prognosis
Tend to regress over time. For locally aggressive lesions, surgical resection is often curative although recurrence has been reported.
Complications
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
Related Radiopaedia articles
Bone tumours
The differential diagnosis for bone tumors is dependent on the age of the patient, with a very different set of differentials for the pediatric patient.
-
bone tumors
- bone-forming tumors
- cartilage-forming tumors
- fibrous bone lesions
- bone marrow tumors
- other bone tumors or tumor-like lesions
- adamantinoma
- aneurysmal bone cyst
- benign fibrous histiocytoma
- chordoma
- giant cell tumor of bone
- Gorham massive osteolysis
- hemangioendothelioma
- haemophilic pseudotumor
- intradiploic epidermoid cyst
- intraosseous lipoma
- musculoskeletal angiosarcoma
- musculoskeletal hemangiopericytoma
- primary intraosseous hemangioma
- post-traumatic cystic bone lesion
- simple bone cyst
-
skeletal metastases
- morphology
- location
- impending fracture risk
- staging
- approach
- describing a bone lesion
- differentials