Ameloblastic fibro-odontoma in an unusual area of the maxilla : Two Case Reports

517 ISSN Online 0719-2479 www.joralres.com © 2019 Abstract: Ameloblastic fibro-odontoma (AFO) is a mixed odontogenic tumor, which has an epithelial and mesenchymal component. It can be observed in imaging tests as a radiomixed lesion, with some authors claiming it represents only the predecessor of an odontoma. Epidemiologically, it appears between the second and third decade of life, predominantly in males and with a predilection for the posterior area of the mandible. This lesion presents a good prognosis and it responds well to enucleation by curettage with a low rate of recurrence. In the present article, two cases of ameloblastic fibro-odontoma in an unusual region of the maxilla are presented.


INTRODUCTION.
AFO is a benign tumor with a mixed origin that has a mesenchymal and epithelial component, forming mineralized tissues and is less common than ameloblastic fibroma (AF). 1,2 Both the odontoma and the AFO present similar characteristics 3 and some authors refer that the AF only represents the predecessor stage of an odontoma 4 while others like Ruiz et al., 5 disagree, affirming that the AFO is a AF variant which occurs together with an odontoma, since the latter is completely radiolucent in the imaging.
The AFO appears between the first and second decade of life, mainly affecting males between 9 to 15 years of age. Some authors state that the most common site for this type of lesions is mainly the posterior region of the mandible (52% -62%) associated with an impacted tooth. 6-8 Its histologic structure consists hypodense pericoronary space was observed, suggesting a dentigerous cyst as a diagnostic impression and welldefined hyperdense multilocular foci, associated with a composite odontoma, contemplating a hybrid lesion ( Figure 1A).
In a surgical meeting consisting of oral surgery and orthodontics, we decided to perform enucleation of the lesion and allow a spontaneous canine eruption due to incomplete development of the root; otherwise, canine traction would be performed posteriorly. Once the patient signed an informed consent form, complete enucleation of the lesion was performed under local anesthesia, revealing a soft and brown consistency.
A sample was sent for histopathological analysis with diagnostic impression of dentin cyst, ameloblastic fibroma, composite odontoma and complex odontoma.
The pathology report shows that there is a lesion consisting of islands of inactive odontogenic epithelium surrounded by connective tissue in myxoid areas. Areas of mineralized tissue reminiscent of cementum are identified, in addition to dental structures, enamel, dentin and pulp tissue ( Figure 1B y Figure 1C).
At the 6-month post-surgical check-up, circumcoronary bone neoformation with eruption in an oblique direction was evident, and it was determined that orthodontics should be performed, leaving adjacent lateral teeth free to avoid reabsorption, and canine traction with orthodontic button. of thin strands and cords of cubic odontogenic epithelial cells, embryonic fibrous connective tissue and primitive odontogenic epithelium, simulating the stellate reticulum which rests on embryonic connective tissue containing randomly oriented fibroblasts, widely spaced. 9 As an encapsulated lesion, AFO is non-invasive and easily removed in most cases. The treatment consists of conservative surgery that can be enucleation by curettage; however, for large lesions, bloc resection is suggested to avoid recurrence. 10 The aim of the present clinical cases is to inform that the imaging characteristics of certain sites of the maxilla should not be considered highly conclusive for a diagnosis, despite the fact that it can be compared to any other type of pathology according to imaging patterns and epidemiological features.

CASE REPORT 1
14 year-old boy presented to our consultation on an orthodontic referral due to a slight increase in volume with approximately 13 months of evolution in the left canine site with persistence of deciduous teeth and absence of permanent ipsilateral canine being asymptomatic.
Upon X-ray examination, a radiomixed lesion of approximately 13.5mm in diameter was found in the upper left canine site with the impaction of a permanent canine with preservation of the cortex and without radicular displacement or reabsorption of adjacent teeth. Upon tomographic imaging, an impacted canine with a  CASE REPORT 2 12 year old female patient attending oral surgery consultation for delayed eruption in canine, lateral and central upper right region, with persistence of canine and lateral deciduous ipsilateral. During clinical examination palpation of a tumor lesion of stony consistency located in the upper right dental arch occurred, with normochromic mucosa covering it, with respect to the adjacent mucosa, asymptomatic, approximately 2cm in diameter, of unknown evolution time and etiology, whose presumptive diagnosis was odontoma.
Tomographically, a hypodense unilateral image of approximately 25mm x 20mm was evident, in which lateral and central upper right canines, at Nolla 9 stage, are included; in addition, multiple hyperdense images of varied dimensions are observed, with the appearance of denticles and amorphous content, with the presence of lateral supernumerary (Figure 2A, Figure 2B and Figure 2C). After signing informed consent by the legal representative, and under local anesthesia, we proceed to perform exodontia of deciduous teeth and enucleation of the content of the lesion, of dark brown color and soft consistency about 0.3cm, which was deposited in 10% formaldehyde for anatomopathological study with diagnostic impressions of complex odontoma, cystic odontogenic tumor and adenomatoid odontogenic tumor.
The histopathological report informs a benign mesenchymal lesion composed of a proliferation of spindle cells with tapered ends, resting on a lax matrix with myxoid changes.  Small light tubular structures are recognized, covered by a double layer of cubic cells without cytological atypia. The lesion is covered by a stratified cubic epithelium of usual morphology, without evidence of necrosis foci or mitosis ( Figure 3A and Figure 3B) At one month follow-up, the evolution showed coronary bone neoformation. The patient was followed-up at 8 months, when central, lateral and upper right canine incisors are observed, which are in traction to the adequate position ( Figure 4A and Figure 4B).

DISCUSSION.
The AFO is a mixed odontogenic tumor of rare appearance, which is accompanied by structures similar to teeth. It can interrupt tooth eruption or displace affected teeth, but the teeth involved remain vital without root resorption. 11 Radiographically, a well-defined radiolucent area is evident, which contains a variable amount of radiopaque material. The histopathological component confirms epithelial cords within a primitive cellular ectomesenchyme that simulates dental papilla, dentin and enamel. 12 In a study of 108 lesions of this type, Kirjavainen et al.,14 reported that they occurred between the ages of 6.3 and 9.6 years with an incidence rate of 1:1.65 in female to male patients, up to age 20, with a predilection for the posterior mandibular area in the molar region, associated with an unerupted tooth in 94% of cases, a recurrence rate of 6% and a good prognosis. 13, 15 On the other hand, Sardana et al., 16 state that the incidence is practically the same for both jaws, with greater frequency in the posterior region.
Nayak et al., 17 and Alani et al., 18 reported one case of AFO in the anterior region of the maxilla, and one with involvement of the maxillary sinus, respectively, with retained teeth and intra-and extra-oral volume changes, highlighting the similarity to the cases presented here.

CONCLUSION.
The development process of dental organs has a great potential to lead to pathologies in any region of the jaws regardless of the site of predilection of certain neoplasms, therefore, other pathological processes should not be ruled out despite a low incidence rates in certain sites. It is important to take into account the chronology of dental eruption in relation to the age of the patients, in relation to the appearance of new tumor lesions associated with retained teeth, as in the present cases.