Central odontogenic fibroma of maxilla: A case report

Introduction

Central odontogenic fibroma (COF) is a rare, benign, mesenchymal odontogenic tumor comprising 0.1% of all odontogenic neoplasms. World Health Organization (WHO) defines COF as a neoplasm made of mature fibrous connective tissue with variable amounts of inactive-looking odontogenic epithelium, with or without the evidence of calcification.¹ The 3^rd edition of the WHO classification of odontogenic tumors in the year 2005 divided COF into two histological types: the simple odontogenic fibroma (epithelium poor) and the complex odontogenic fibroma, more commonly known as the WHO type (epithelium rich).² However, in the 2017 WHO classification (4^th edition), the subtypes were excluded due to poorly defined and documented epithelial poor type of COF.

COFs pose a diagnostic dilemma to clinicians as well as pathologists. The clinical and radiological features of this tumor are not distinct. It has a close resemblance with other odontogenic and/or non-odontogenic tumors and cannot be distinguished either clinically or radiographically. The differential diagnosis is based on the histopathological examination which is quite challenging due to the rarity of this entity.

In this case report, we narrate a case of a 63-year-old female patient with swelling in the left maxilla which was later diagnosed as a central odontogenic fibroma. 

Case Description

A 63-year-old female, with no significant medical history, reported the complaint of missing teeth in her upper and lower arches and wanted to get her teeth replaced. However, on clinical examination, a diffuse swelling was evident on the left side of the upper jaw in the maxillary tuberosity region. Buccal and palatal cortical plate expansion was seen in the left maxillary alveolar ridge extending from the 26 to 28 region (Figure 1). On palpation, the swelling was bony and hard in consistency with a smooth surface. Surprisingly, the patient was unaware of the swelling and had no pain or discomfort in that region. Orthopantomogram (OPG) was advised which revealed the presence of a spherically dense radiopaque mass (supposedly impacted tooth number 28) in the left maxillary sinus region measuring approximately 1.5x1.5cm. This dense mass at its distal aspect was associated with an expansile unilocular lesion with a corticated border measuring approximately 3.0x3.0cm. The lesion had a mixed radiopaque/radiolucent appearance (Figure 2). Radiographic differential diagnosis revealed calcifying epithelial odontogenic tumor (CEOT) and dentigerous cyst. 

An incisional biopsy was performed under local anesthesia. On macroscopic examination, 12 soft tissue bits of the specimen were received which were whitish with the largest tissue bit measuring about 1.2×0.4×0.2cm (Figure 3).

The microscopic examination of the Hematoxylin and Eosin stained section revealed mature, cellular connective tissue stroma with few inactive-looking odontogenic islands in the form of nests and strands (Figure 4A). The odontogenic epithelial cells were cuboidal and ovoid with hyperchromatic nuclei (Figure 4B). A few focal areas of eosinophilic calcifications were also noted (Figure 4C). Due to the lack of intercellular bridges between the odontogenic epithelial cells, basophilic liesegang calcifications, and amyloid deposition in the connective tissue, CEOT was ruled out. Despite the ambiguous clinical and radiographic pictures, thorough histopathological evaluation helped to arrive at the diagnosis of COF. The patient was not willing to undergo further treatment, hence the final definitive diagnosis will, unfortunately, remain a mystery for the excisional biopsy findings that could have revealed a different picture. The rehabilitation was done with the construction of a denture, the patient is on regular follow-ups for foreseeing any changes in the tumor growth.

Discussion

Odontogenic fibroma (OF) is topographically categorized into two types: the central or intraosseous type and the peripheral or extraosseous type. ³

The peripheral odontogenic fibroma usually occurs in the mandibular gingiva and is more commonly encountered than the central type.⁴ Of all the odontogenic tumors, central odontogenic fibroma has the most poorly defined parameters. There is a lack of unanimity regarding the nature of this lesion due to the rarity of the cases.⁵

COF can appear at any age with a mean age of 40 years and have a slight predilection for females. COFs occur equally in the maxilla and the mandible. The most common locations are the anterior maxillary regions (71%) and posterior mandibular regions (73%).⁶ Radiographically, the lesions present as unilocular/ multilocular radiolucencies with well-defined borders sometimes associated with an impacted tooth. A mixed radiolucent and radiopaque lesion is found in 10.7% of the cases in the mandible.⁷ In the present described case, we encountered a unilocular lesion with sparse calcifications, rendering it a mixed radiolucent and radiopaque appearance.

In 1980, Gardner classified COF histologically into three different groups:

1) Hyperplastic dental follicle

2) Simple COF comprising of fibrous type of connective tissue with nests of odontogenic epithelium

3) The WHO-type COF with features of dysplastic dentin or cementum-like tissue and varying amounts of odontogenic epithelium

However, Gardner emphasized that hyperplastic dental follicles cannot be considered COF. The WHO type of COF was described by Doyle et al. as a complex odontogenic fibroma to which Gardener concurred.⁸

However, the 4^th edition of the WHO classification of odontogenic tumors (2017) eliminated the terms ‘simple’ and ‘complex’ and suggested the usage of the term central odontogenic fibroma, unanimously.¹ Hence, in the present case, a diagnosis of ‘central odontogenic fibroma’ was given.

Histologically, differential diagnosis of COF includes ameloblastic fibroma (AF), desmoplastic fibroma (DF), hyperplastic dental follicle, and odontogenic myxoma. Desmoplastic fibroma has a very aggressive behavior and is devoid of epithelial islands and has myofibroblasts in the connective tissue.⁹ Ameloblastic fibroma, on the other hand, is composed of active odontogenic islands, with connective tissue being highly cellular and embryonic looking.⁵ COF with an unerupted tooth can be mistaken as a hyperplastic dental follicle. Nevertheless, the presence of large odontogenic islands and mature connective tissue in COF can help in differentiating it from the hyperplastic dental follicle.⁵ In contrary to COF, epithelial islands are rarely seen in odontogenic myxoma. The latter contains spindle-shaped, stellate cells in a loose myxoid stroma.⁷ One can arrive at a diagnosis of COF after the exclusion of different lesions.

COFs are treated by conservative surgery. Recurrence is rare and is seen in cases with an incomplete curettage, otherwise, the prognosis of the tumor is good.¹⁰

It is of utmost importance to emphasize the rarity of odontogenic fibroma and that it should not be missed due to its ambiguous clinical and radiographic features. As with the case presented, diligent histological evaluation along with consideration of the differential diagnosis helped to arrive at the final diagnosis.

Conflict of Interest

None