Monday 10 April 2006
Definition: Ameloblastic fibroma is a proliferation of immature odontogenic mesenchymal and epithelial cells. No mineralization or production of enamel, dentin or cementum is seen.
December 2007, Case 712-1, Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
There is no gender predilection and most patients are under 20 years of age.
It may occur in any tooth bearing site but is more common in the premolar-molar region of the mandible.
Radiographically they are well demarcated, well corticated radiolucencies that may be unilocular or multilocular.
Microscopically they are composed of young basophilic fibromyxoid tissue. There are islands, cords and strands of ovoid, cuboidal and occasionally columnar epithelium. There is no evidence of mineralization.
Treatment is conservative surgical enucleation and the recurrence rates are very low.
Ameloblastic fibroma occurs most commonly in young patients in the 1st and second decades of life. Occasional cases are seen in older patients.
Males are slightly more affected than females. As per one of the large series, AF comprises about 6.5% of central (intraosseous) odotogneic tumors. They can also occur as peripheral (extraosseous) odontogenic tumors. Although odontogenic tumor is rare in children, AF belong to the very few that are mostly seen in children and young adults.
AFs are often asymptomatic when they are small and present as swelling of the jaws when they are large. About 70% of the tumors occur in the premolar and molar region of the mandible and the premolar and molar region of the maxilla is the next most common site. Less than 10% of them occur in the canine and incisor regions. Rare cases have been reported as lesions of the maxillary sinus.
Radiographically, they often occur as a well defined or sclerotic unilocular or multilocular radiolucent lesion and about three quarter of them are associated with an unerupted tooth.
The smaller tumors tend to be unilocular. Rare ameloblastic fibrosarcoma and ameloblastic carcinoma arising from amdloblastic fibroma have been desciribed. Hybrid tumor comprised of AF and other odontogenic tumor do occur. As per one of the studies, the recurrence rate is about 33%.
In general, conservative excision with follow up is adequate initial treatment. More aggressive surgery should be considered for recurrent lesions.
Grossly, ameloblastic fibromas occur as solid, soft tissue mass with or without a capsule.
Histologically, there are anastomosing cords and of low-histologic grade epithelium that resemble odotogenic epithelium embedded within a background of cellular mesenchyma that resembles primitive dental papilla.
The mesenchymal component is composed of plump stellate cells and ovoid cells in a loose matrix with little collagen deposition albeit diffuse hyalinization can be seen.
The anastomosing cords are often two-cell thick cuboidal or columnar epithelium. Less commonly, the epithelial component appears as small, discret islands characterized by a peripheral rim of columnar cells surround a central core of stellate cells and such arrangement mimics the follicular stage of developing enamel organ.
Microcyst formation is rarely seen in these islands and is a feature that distinguishes AF from follicular variant of ameloblastoma. Hyalinization around the epithleial cords and islands may be present.
Ameloblastic fibroma belongs to a family of tumor with mixed proliferating odontogenic epithelium and a cellular mesenchymal component that resembles dental papilla.
The interactions of these two components lead to the deposition of enamel and dentin and formation of structures that may resemble tooth formation.
Members of this family include:
ameloblastic fibrosarcoma (ameloblastic sarcoma)
This family of tumor ranges from true neoplasm to hamartoma with odontoma as an example of hamartomatous lesion.
Clinical and imaging information are critical for the correct diagnosis as histologic features alone are difficult for making the correct diagnosis in some cases.
While the majority of ameloblastoma fibromas are true neoplastic lesion that is capable to recur and, in rare situations, undergo malignant transformation, a small number of ameloblastic fibroma that occurs in young children do show evidence of maturation and suggest that they are the early or primitive stage of a developing odontoma.
- particularly those with desmoplastic changes.
ameloblastic fibrosarcoma (ameloblastic sarcoma)
Cytogenetics: no data
CGH: no data
LOH: no data
- odontogenic tumors
- ameloblastic fibrosarcoma
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