cemento-ossifying fibroma

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Cemento-ossifying fibroma (COF) are rare, benign neoplasms that usually arise from the mandible or maxilla. They most often arise from the tooth bearing areas of these bones.

Terminology

In the 2005 WHO histological classification of odontogenic tumors, this tumor is referred to as "ossifying fibroma" but in this article, the term cemento-ossifying tumor is used to differentiate from peripherally occurring ossifying fibromas.

Other synonyms of cemento-ossifying fibroma besides ossifying fibroma include :

cementifying fibroma
juvenile (active/aggressive) ossifying fibroma
- discussed separately because of differences in distribution/epidemiology

There is confusion in the literature about the nomenclature to use when describing these lesions. Moreover, confusion exists regarding its relationship to other similar entities with various definitions and debate as to whether it is of odontogenic or nonodontogenic osseous origin , although the 2005 WHO classification currently lists it as a "bone-related tumor" .

Epidemiology

Cemento-ossifying fibromas are most frequently diagnosed during the third and fourth decades with a distinct female predilection (F:M = 2-5:1) . Occasionally, they are identified in children, in which case they are a more aggressive variant and are known as juvenile aggressive cemento-ossifying fibromas (discussed separately) .

Clinical presentation

Clinical presentation is with a solid mass, usually arising from the mandible (62-89%) or maxilla. Most frequently they arise from the premolar region of the mandible (77%) . Teeth are often displaced by the growing mass. Other locations within the head and neck have been described .

Pathology

These tumors are composed of fibrous tissue, calcified tissue resembling bone and/or cementum . The bone-like component is predominant reminiscent of woven bone and is found in more 'mature' lesions . In some instances, this entity has been divided into cementifying fibroma and ossifying fibroma depending on the relative amounts of the tumor's constituent tissues. However, in most cases both features are present, warranting the generic term cemento-ossifying fibromas .

They are thought to arise from the periodontal ligament, accounting for the usual vicinity to teeth .

Radiographic features

Plain radiograph and CT

Cemento-ossifying fibromas are usually well-circumscribed masses which expand the underlying bone. They are usually small but can become large. This is particularly the case when they arise from the maxilla or paranasal sinuses because there is more room to expand . They are initially lucent on x-ray with soft tissue attenuation on CT. As they mature, they gradually develop increasing amounts of calcification/ossification as they mature. They usually expand the bone without cortical breach .

Following administration of contrast, the soft tissue component usually enhances on CT .

MRI

Although masses are composed of a mixture of calcified and non-calcified soft-tissue, as the later is predominantly fibrous, the whole mass is largely of low intensity on MRI .

T1
- intermediate to low signal
- focal regions of higher signal may represent fatty marrow in ossified components
T2: low signal
T1 C+ (Gd): soft-tissue component may demonstrate some enhancement

Treatment and prognosis

Surgical excision is the treatment of choice, and it usually requires bone grafting or reconstructive surgery . Recurrence following complete excision is generally considered to be uncommon . However, in some series, it has been reported to be as high as 28% .

Differential diagnosis

The differential is essentially that of a lesion of the mandible or lesion of the maxilla (depending on location and degree of mineralization). Some entities worth considering include :