Volume 1, Issue 3 , Pages 200-203, September 2006
Ameloblastic fibro-odontoma: Report of a case presenting an unusual clinical course
Article Outline
Summary
Ameloblastic fibro-odontoma has been defined by the World Health Organization (WHO) as “a lesion resembling ameloblastic fibroma” which also shows inductive alterations that lead to the formation of enamel and dentin. It is a rare lesion and is classified among odontogenic lesions as an epithelium tumor containing ectomesenchyme with or without the formation of dental hard tissue. We report here the case of a unusual ameloblastic fibro-odontoma seen in a 4-year-old boy and discuss the clinical, radiographic, histopathologic and therapeutic aspects of this tumor.
Keywords: Ameloblastic fibro-odontoma, Odontogenic lesion, Enamel, Dentin
1. Introduction
Ameloblastic fibro-odontoma (AFO) has been defined by the World Health Organization (WHO) as “a lesion resembling ameloblastic fibroma which also shows inductive alterations that lead to the formation of enamel and dentin” [1], [2], [3]. It is a rare lesion and is classified among odontogenic tumors as a epithelium tumor containing ectomesenchyme with or without the formation of dental hard tissue [4].
Ameloblastic fibro-odontoma mainly affects patients in the first two decades of life and can be characterized as an almost exclusive lesion of children and adolescents. It preferentially affects male patients and is usually located in the posterior region of the mandible [5].
Clinically, the tumor is painless and of slow growth, with tumor expansion being observed. Most tumors are associated with the crown of an unerupted tooth, a fact that guides the diagnosis of the lesion. The size of the tumor shows marked variation, ranging from lesions detectable only microscopically to giant tumors consisting of extensive calcified masses [2].
Radiographic analysis reveals a radiolucent, uni- or multilocular lesion with well-defined borders, with radiopaque foci being observed inside the lesion that can assume a density similar to that of dental hard tissues [1], [6].
Histopathologically, ameloblastic fibro-odontoma consists of chains, nests or islets of odontogenic epithelium scattered within a primitive ectomesenchyme. Calcified structures consisting of dentin- or osteodentin-like material, as well as an enamel matrix can be identified [6], [7].
We report here the case of a highly aggressive ameloblastic fibro-odontoma seen in a 4-year-old boy and discuss the clinical, radiographic, histopathologic and therapeutic aspects of this tumor.
2. Case report
Patient P.V.D.S., a 4-year-old white boy, presented at the Dental Clinic of the Faculty of Dentistry, Federal University of Rio Grande do Norte, with a volume increase in the right anterior region of the maxilla. According to the responsible person, the lesion was asymptomatic and of slow growth, and no information was available regarding the exact time of onset. Intraoral clinical examination confirmed the reported volume increase which extended from the region of the right lateral incisor to the posterior region of the maxilla with no changes in the color of the overlying mucosa. Panoramic radiography revealed an extensive, circumscribed, unilocular radiolucent lesion with radiopaque foci inside the lesion, which involved almost the entire right hemi-arch of the maxilla and even pushing back distally tooth 55 (Fig. 1).
Fig. 1.
Panoramic radiography revealed an extensive, circumscribed, unilocular radiolucent lesion with radiopaque foi inside the tumour (arrow).
The initial clinical diagnosis was myxoma and the patient was submitted to surgical excision of the lesion after access ostectomy under general anesthesia. Histopathologic examination showed a benign ectomesenchymal neoplasia of odontogenic origin characterized by the proliferation of islands, nests and cords of epithelial cells that exhibited a palisaded arrangement at the periphery and centrally a loose arrangement resembling the stellate reticulum of the enamel organ. Squamous metaplasia was observed at the periphery in some of these islands. The mesenchyme of the lesion was richly cellularized, containing spherical, stellate or spindle-shaped cells (Fig. 2, Fig. 3, Fig. 4). Amorphous eosinophilic material compatible with dentinoid material (Fig. 3, Fig. 4, Fig. 5), as well as basophilic material compatible with rudimentary enamel, was observed on various planes of the specimen (Fig. 6). Based on these characteristics, the histopathologic diagnosis was ameloblastic fibro-odontoma and the patient is currently under observation.
Fig. 2.
Photomicrograph of the lesion: proliferation of islands, nests and cords of epithelial cells in the mesenchyme richly cellularized (H and E, 40×).
Fig. 3.
Photomicrograph of the lesion: amorphous eosinophilic material compatible with dentinoid mass (H and E, 100×) (arrow).
Fig. 4.
Photomicrograph of the lesion: islands of epithelial cells that exhibit a palisaded arrangement at the periphery (H and E, 100×) (arrow).
Fig. 5.
Photomicrograph of the lesion: islands of epithelial cells that exhibit a palisaded arrangement at the periphery (H and E, 200×) (arrow).
Fig. 6.
Photomicrograph of the lesion: basophilic material compatible with rudimentary enamel (H and E, 200×) (arrow).
3. Discussion
Ameloblastic fibro-odontoma is a relatively rare odontogenic tumor whose etiopathogenesis has been a matter of controversy. According to some investigators, ameloblastic fibroma, FOA and compound and complex odontoma represent evolutive stages of the same lesion. However, the WHO classifies the reported tumors into distinct entities [8], [9].
The differential diagnosis between AFO and ameloblastic fibroma is made based on the presence (AFO) or absence (ameloblastic fibroma) of elements indicative of tooth germ differentiation (enamel or dentin) [3]. Slootweg (1981) concluded that AFO and complex odontoma might be distinct evolutive stages of the same lesion. However, the WHO did not agree with the hypothesis of this author and classified the two lesions as distinct entities, thus ruling out the hypothesis that both lesions correspond to hamartomas [3].
The case reported in the present study supports the hypothesis of a distinction between ameloblastic odontoma and complex odontoma, since the patient presented a lesion of highly aggressive behavior and was affected at a young age, thus indicating a neoplastic behavior for AFO, a fact reported by Yagishita et al. (2001).
Histologically, AFO shows the characteristics of an immature complex odontoma, including an irregular arrangement of enamel- and dentin-like calcified structures, as well as ectomesenchymal tissue [6], [10], [11]. In the present case, the ectomesenchymal portion was found to be richly cellularized, containing cells of distinct shapes, i.e., spherical, stellate or spindle-shaped. This cellularity may explain the more aggressive biological behavior observed here, as well as for cases reported by Reichart et al. (2004), who were also highly aggressive and showed intense cellularity in the ectomesenchymal portion. In addition, an intriguing characteristic was identified in some odontogenic epithelial islands, which occasionally showed peripheral cell squamous metaplasia.
Recurrence or local invasion is normally not observed in ameloblastic fibro-odontoma, with the tumor being treated by surgical enucleation. However, lesions with a neoplastic behavior extensively compromise involved bone, a fact justifying the need for a more radical surgical procedure as observed in those cases reported by Piette et al. (1990) [12] and Hu et al. (2006) [13]. These authors reported cases of a voluminous maxillary AFO where it was necessary to execute a partial maxillectomy and the signs of recurrence in 12 and 18 months follow-up, respectively were absent. Nevertheless, since the present case affected a 4-year old patient, the non-radical treatment of the lesion was choose, and no recurrence was observed after 7 months.
Surgery enucleation of large AFO affecting two young patients, one with 9 and other with 12 years old, was also performed to Reichart et al. (2004), and after 3 years no recurrences were observed. However, Friedrich et al. (2001) observed recidivant tumor in a 10-year old boy after 18 months of the same surgical intervention.
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PII: S1871-4048(06)00058-X
doi:10.1016/j.pedex.2006.05.004
© 2006 Elsevier Ireland Ltd. All rights reserved.
Volume 1, Issue 3 , Pages 200-203, September 2006
