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Cemento-ossifying fibroma

A cemento-ossifying fibroma (COF) is a rare benign neoplasm that usually arises from the mandible and maxilla. They most often arise from the tooth bearing areas of these bones.

There is confusion in the literature about the nomenclature to use when describing these lesions; see the WHO classification of odontogenic tumours. Moreover, confusion exists regarding its relationship to other similar entities with various definitions and debate as to whether it is of odontogenic or non-odontogenic osseous origin 1-6

For the purpose of this article, the term cemento-ossifying fibroma is used synonymously with (central) ossifying fibroma (of the head and neck). This takes into account the fact that the demographics, radiographic appearances and location are identical. The nomenclature has arisen predominantly due to the variable amounts of bone-like material and cementum-like material (see below) 6.

Although juvenile aggressive cemento-ossifying fibroma (also known as juvenile ossifying fibroma) is most likely a variant of cemento-ossifying fibroma, it is discussed separately. This is because of the difference in distribution and demographics 5.

Cemento-ossifying fibroma should not be confused with peripheral ossifying fibroma which is a reactive non-neoplastic lesion.

Epidemiology

Cemento-ossifying fibromas are most frequently diagnosed during the third and fourth decades with a distinct female predilection (F : M = 2 to 5 : 1) 1,3,6. 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) 3,5.

Clinical presentation

Clinical presentation is with a solid mass, arising usually from the mandible  (62 - 89%) 3 or maxilla. Most frequently they arise from the premolar region of the mandible (77%) 3. Teeth are often displaced by the growing mass. Other locations within the head and neck have been described 1.

Pathology

These tumours are composed of fibrous tissue, calcified tissue resembling bone and/or cementum 1,3. The bone-like component is predominant reminiscent of woven bone and is found in more 'mature' lesions 1. In some instances, this entity has been divided into cementifying fibroma and ossifying fibroma depending on the relative amounts of the tumour's constituent tissues. However, in most cases both features are present, warranting the generic term cemento-ossifying fibromas 1.

They are thought to arise from the periodontal ligament, accounting for the usual vicinity to teeth 3.

Radiographic features

Plain film 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 1-3. 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 3

Following administration of contrast, the soft tissue component usually enhances 1.

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 1.

  • T1
    • intermediate to low signal
    • focal regions of higher signal may represent fatty marrow in ossified components
  • T2 : low signal
  • T1 C+ (GAD) : 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 1,3. Recurrence following complete excision is generally considered to be uncommon 1,6. However, in some series, it has been reported to be as high as 28% 3.

Differential diagnoses

The differential is essentially that of a lesion of the mandible or lesion of the maxilla (depending on location and degree of mineralisation). Some entities worth considering include 1-3:

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