Ossifying fibroma

Findings

Axial CT bone windows (Figure 1 and Figure 2) show an expansile lesion of the left maxillary sinus with dense osseous material on the periphery and low attenuation fibrous center. Coronal reformats (Figure 3) demonstrate mass effect on the left orbit. Sagittal reformats (Figure 4) show scattered foci of soft tissue density among ossified areas.


Diagnosis: Ossifying fibroma


Fibro-osseous lesions of the paranasal sinuses are a broad spectrum of bony disease with fibrous dysplasia, ossifying fibroma, and osteoma being distinct entities that lie along a continuum from the least to the most bony content. They have similar appearance and makeup; however, their clinical implications vary.

Osteoma is the most common tumor of the paranasal sinuses. The vast majority (95%) of sinonasal osteoma are found in the frontoethmoidal region. Most frequently, osteomas are asymptomatic and are discovered incidentally

Fibrous dysplasia (FD) is a slow-growing fibro-osseous lesion that can be located in the paranasal sinuses. It can be mono- or poly-ostotic. Fibrous dysplasia affects children and characteristically “burns out” during puberty. It is deforming but not destructive.

Ossifying fibroma (OF) is the most concerning of the fibro-osseous lesions in the paranasal sinuses as it can be locally destructive. It is also known as cemento-ossifying fibroma; psammomatoid ossifying fibroma, and juvenile-aggressive ossifying fibroma. It is characteristically monostotic and the most common craniofacial site is the mandible (75%). However, it is considered more aggressive when found outside the mandible.

Histologically, ossifying fibroma is an encapsulated tumor with matrix of randomly distributed mature, lamellar bone spicules mixed with fibrous stroma.

Radiographically, it is a sharply circumscribed, expansile lesion with an eggshell rim and a central low attenuation fibrous center. Ossifying fibroma is locally aggressive and can absorb tooth roots, whereas fibrous dysplasia usually encompasses the healthy roots.

Ossifying fibroma usually presents in young adults. It is generally asymptomatic and found incidentally. The juvenile variant may show aggressive, locally destructive behavior and cause compression of vital structures, severe pain or facial pain.

Because of the aggressive and locally destructive nature of ossifying fibroma, complete surgical excision is recommended.