Ossifying fibroma of the mandible

Clinical History

A 54-year-old man presented to the maxillofacial surgeon with a slowly increasing swelling of the lower left jaw for more than 6 months. The lesion was painless, hard and immobile on palpation.

Imaging Findings

A cone beam CT (CBCT) of the mandible showed a well-circumscribed osseous lesion in the left mandible, measuring 46 x 22 x 33 mm. The lesion was radiopaque with a ground glass appearance. There was bone expansion with cortical thinning but absence of cortical breakthrough and no periosteal reaction (Fig.1-4). The mandibular canal was displaced inferiorly.
A biopsy was performed and subsequent histopathological examination showed cellular connective tissue with an osteoblastic rim on the surface of woven bone intermingled with a fibrous component without atypia (Fig. 5). Diagnosis of ossifying fibroma was made and the lesion was partially resected.

Discussion

Ossifying fibroma is a benign neoplasm composed of fibrous tissue and mineralized material. The previously used term cemento-ossifying fibroma was renamed as ossifying fibroma according to the revised WHO classification (2005) [1, 2].
It is thought that ossifying fibromas of the jaw arise from the periodontal ligament but this remains controversial as similar lesions may appear in bones that lack this structure. Some authors suggest a possible relationship with previous trauma as a triggering factor [3]. The craniofacial bones are the most frequently involved with a predilection for the region inferior to the molars and premolars of the mandible. Ossifying fibromas are most frequently diagnosed during the third and fourth decades with a marked female predilection (female:male ratio: 4:1). A juvenile variant, ore aggressive, exists that most commonly affects boys younger than 15 years [1, 3, 4].
The clinical presentation usually consists of a painless slowly growing mass. Lesion expansion may result in tooth displacement, root resorption and facial asymmetry if untreated. The mass is covered with normal mucosa. Lymphadenopathy is not seen [3-6].
Different radiographic patterns have been described depending on the amount of mineralized tissue. Most frequently the lesion is mixed radiopaque-radiolucent and less commonly either radiolucent or radiopaque. The degree of opacity of the lesion depends on its age. With maturation the lesion becomes more radiopaque due to progressive matrix mineralization. The lesion is usually unilocular although infrequently a multilocular appearance is seen. The main differential diagnosis consists of fibrous dysplasia if the lesion has a ground-glass attenuation. The margins of the lesion are always well demarcated whereas fibrous dysplasia may have ill-defined borders. The mandibular canal may be displaced inferiorly while in fibrous dysplasia the canal may be displaced in any direction. Usually the lesion displays concentric growth and buccolingual expansion. Tooth displacement and root resorption are seen in larger lesions [5, 7, 8].
The recommended treatment is complete surgical resection or enucleation since incomplete resection has a high recurrence rate. In our case complete resection was impossible due the proximity of the lesion to the mandibular canal. Surgical treatment may require bone grafting or reconstructive surgery. The estimated recurrence rate after appropriate surgical removal is 12% [5, 7].

Differential Diagnosis List

Final Diagnosis

Ossifying fibroma

URL:	https://www.eurorad.org/case/14188
DOI:	10.1594/EURORAD/CASE.14188
ISSN:	1563-4086