Ameloblastic fibroma (AF) is a benign odontogenic tumor predominantly affecting young patients, typically around 15 years of age. While most cases occur in younger individuals, it’s important to note that approximately 25% of cases can be found in patients older than 22, highlighting the necessity for broad diagnostic consideration across age ranges, especially in populations with limited access to routine dental care.
Studies suggest a slight male predilection for ameloblastic fibroma. The posterior mandible is the most common location, although larger tumors can extend into the anterior mandible. A notable characteristic, often seen but not present in all cases, is the association of AF with an impacted tooth, potentially hindering tooth eruption. Clinically, ameloblastic fibroma often presents with insidious growth, with swelling being the most frequent sign. However, symptoms like ulceration and pain do not rule out AF, as these have been documented in reviews of ameloblastic fibroma cases. Interestingly, about 20% of ameloblastic fibromas are detected incidentally during routine dental radiographs, as was the case in the instance described in the original article. In that specific case, the tumor’s location between the roots of the mandibular second premolar and first molar caused a noticeable diastema.
Radiographically, ameloblastic fibroma typically appears as a well-defined radiolucent lesion, which can be either unilocular or multilocular, averaging about 4.0 cm in size. When evaluating such lesions, the differential diagnosis of ameloblastic fibroma becomes critical. Several entities must be considered, including ameloblastoma, odontogenic myxoma, keratocystic odontogenic tumor (KCOT), and central giant cell lesion (CGCL). In the case previously mentioned, the stepladder pattern created by thin septa was reminiscent of odontogenic myxoma. However, odontogenic myxoma is more prevalent in patients in their third and fourth decades of life and may exhibit diffuse calcifications, features not typical of AF. While asymptomatic ameloblastic fibromas are usually unilocular radiolucencies, the described case was uniquely a multilocular mixed lesion, a less common presentation of ameloblastic fibroma.
Image alt text: Radiograph showing a multilocular radiolucent lesion in the mandible, suggestive of ameloblastic fibroma.
In the context of mixed radiographic lesions, the differential diagnosis of ameloblastic fibroma expands further. Considerations should include ossifying fibroma, extra-follicular adenomatoid odontogenic tumor (AOT), calcifying cystic odontogenic tumor (CCOT), and calcifying epithelial odontogenic tumor (CEOT). Except for AOT, these tumors are less common in the typical age group for ameloblastic fibroma. A distinguishing radiographic feature often lies in the location of radiopaque foci. In ossifying fibroma, CCOT, and CEOT, these foci are usually centrally located or dispersed throughout the lesion. Conversely, in the described ameloblastic fibroma case, the radiopaque area was peripherally located, likely indicating peripheral bone neo-formation induced by the lesion, resulting in the mixed radiographic appearance. This peripheral radiopacity could also represent an area of less bone resorption compared to the more radiolucent regions. Despite the presence of radiopaque areas radiographically, microscopic analysis revealed no hard tissue formation.
Because ameloblastic fibroma is frequently associated with unerupted teeth, it can initially be mistaken for a dentigerous cyst. Like ameloblastic fibroma, dentigerous cysts are often discovered as incidental radiographic findings. This underscores the importance of routine dental examinations, especially radiographic screenings, in children and adolescents to facilitate early detection and accurate Ameloblastic Fibroma Differential Diagnosis.
Microscopically, ameloblastic fibroma is characterized by odontogenic epithelium proliferating within a myxoid, cellular connective tissue resembling dental papilla. This tissue exhibits varying degrees of inductive changes, but crucially, there is no formation of dental hard tissues. The epithelial component is seen as islands, strands, or projections of odontogenic epithelium, with a peripheral layer of cuboidal or columnar cells and central areas reminiscent of the stellate reticulum. The amount and density of the epithelial component can vary within the same tumor. Cystic degeneration and mitotic activity are rare in ameloblastic fibroma. Histopathologically, the ameloblastic fibroma differential diagnosis includes odontogenic myxoma and odontogenic fibroma. Odontogenic myxoma infrequently shows epithelial islands, contrasting with ameloblastic fibroma. Epithelium-poor odontogenic fibroma presents loose connective tissue, sometimes fibromyxoid, but its epithelial islands are scarce and inactive. Epithelium-rich odontogenic fibroma contains a variable amount of inactive odontogenic epithelial islands, whereas ameloblastic fibroma exhibits islands and strands of neoplastic epithelial cells. Moreover, in epithelium-rich odontogenic fibroma, epithelial islands are embedded in a cellular fibroblastic connective tissue, unlike the specific neoplastic epithelial islands in ameloblastic fibroma.
Image alt text: Histopathological image of ameloblastic fibroma demonstrating odontogenic epithelium within a cellular myxoid stroma.
While malignant transformation of ameloblastic fibroma to ameloblastic fibrosarcoma is rare, careful attention should be paid to mitotic activity, which raises suspicion for fibrosarcoma. Mesenchymal proliferation leading to a reduction in the epithelial component can also indicate malignant change. However, a diagnosis of malignant transformation is typically confirmed by examining primary or recurrent tumors where original ameloblastic fibroma histology is still evident.
Conservative treatment, such as excision followed by curettage, as performed in the described case, is generally considered appropriate for ameloblastic fibroma. Larger or recurrent tumors might necessitate more extensive resection. Reviews indicate a recurrence rate of about 16.3% for ameloblastic fibroma, with malignant transformation to ameloblastic fibrosarcoma occurring in approximately 6.4% of reviewed cases. These statistics underscore the importance of complete tumor excision and long-term clinical and radiographic follow-up, particularly for recurrent cases, which have a higher risk of malignant transformation. It is also important to note that around two-thirds of ameloblastic fibrosarcomas arise de novo.
In conclusion, ameloblastic fibroma, while rare, generally has a favorable prognosis. However, diligent post-treatment follow-up is essential, especially for recurrent tumors. Radiographic examinations are vital complements to routine clinical exams in detecting mandibular lesions. Although uncommon, ameloblastic fibroma should always be included in the differential diagnosis of mixed lesions of the jaws, particularly in children and adolescents. Accurate ameloblastic fibroma differential diagnosis is crucial for appropriate management and patient care.
