Ameloblastoma is a neoplastic lesion that in its early stages does not present signs or symptoms; ages more common in which occurs this lesion are between 20 to 30 years of age, it has no predilection by any gender; their formation can be derived epithelial involved with the formation of teeth. The objective of this review is to present a clinical case of a 14-year-old male patient referral to the Hospital del Niño DIF Hidalgo, which presented volume increased in right hemiarch, diagnostic studies were conducted in which the result was an Unicystic Ameloblastoma of the Mandible, which was addressed through conservative treatment. It is intended that this review will update the knowledge and therapeutic approaches to this disease, assessing tumor location and patient age.
Keywords: Unicystic Ameloblastoma of the Mandible; pediatric patient.
In 1868, Broca is the first person who describes a report of ameloblastoma in the scientific literature. 11 years later, Falkson completed the first detailed histological description. In 1885, Malassez introduces the term "Adamantinoma" which implies that the tumor was formed by a hard tissue 1, which was not met in all cases, so it was left later. Over the years we have used different synonyms to refer to this lesion 2. The Unicystic Ameloblastoma is a low aggressive neoplastic lesion that grows slowly and quietly, which shares macroscopic similarity to the most common odontogenic cyst.
In its early stages this lesion has no signs or symptoms 3. During its evolution is usually destructive and can cause migration, root resorption and the mobility of tooth organs of the region involved. Sometimes it produces cortical expansions, though in most cases this lesion erodes them and invades the soft tissue, which can cause paresthesia. 4, 5, 6
This tumor is the second odontogenic tumor most common 7 and among all the different types of ameloblastoma, the Unicystic represents 6% of all cases 8, 9. In pediatric patients the unicystic ameloblastoma percentage is very high 10, 11. Mosqueda analyzed 349 cases of pediatric tumors. It was obtained that 34.6% of the cases were odontoma type and 23.7% Ameloblastoma type 12. This lesion occurs most commonly among the 20-30 years old and it does not prefer any genre 9, 13.
Ameloblastoma affects most commonly the mandible, by 80%. It affects the region among third molar and the mandibular branch 3,9,1415. When it affects the maxillary region, it predominates its rear zone 4,5,6,7,11.
This lesion is classified into 3 subtypes: a) intraluminal, when tumor cells proliferate into the pathological cavity, b) luminal, the cystic lesion is surrounded by the epithelium of the ameloblastoma and c) mural or intramural, the neoplastic cells infiltrate the fibrous tissue of the cystic wall. Intraluminal and luminal can be treated by enuclation, unlike intramural which should be considered as a solid ameloblastoma because of their infiltration capacity 3,6,10,16,17,18.
Its etiology is still unknown, some authors claim that the formation of ameloblastoma is derived from the epithelium involved with the formation of teeth, which include: the remains of the enamel organ (cell rests of Malassez, and cell rests of Serres), the epithelium of odontogenic cysts, specially the dentigerous and odontoma, abnormalities of the enamel organ in development and epithelial basal cells of the jaws 3,8,14,19. The factors that cause the neoplastic transformation of these epithelial structures are still unknown. Some authors claim that this transformation occurs subsequently to tooth extractions, cystectomy, or other trauma8.
In the past ameloblastoma was classified into solid and cystic, because of this Vickers and Gorlin in 1970, from 10 samples, identified the histopathological changes. These are the changes that were found in the lining epithelium: hyperchromatism in the nuclei of basal cells, palisade arrangement with polarization of basal cells with cytoplasmic vacuolization, with epithelial intercellular spacing, tumor nodules that project in an intraluminal way, epithelium of proliferating ameloblastic lining inside the wall of the conjunctive tissue 20.
Robinson and Martinez suggest that for the diagnosis of a unicystic ameloblastoma is required to be present some of the following characteristics in the lesion: a) Cyst epithelium is homogeneously Ameloblastic; b) An ameloblastic nodule or more do project into the cystic lumen without infiltration of the fibrous wall of cyst by odontogenic epithelium; c) One or more epithelial ameloblastic projections proliferate in the thickness of the connective wall, whether it is follicular type or plexiform type, which may or may not be connected to the epithelial lining of the cyst; d) islands of ameloblastic tissue are present inside the connective wall which is in direct contact with the epithelium of a cyst apparently not neoplastic 21.
According to histology, ameloblastomas are non-encapsulated neoplasm. They categorize into five patterns: a) follicular, it contains islets of epithelial elements in the stroma; b) plexiform, which contains beads of epithelial elements; c) acanthomatous, it might be observed a fluted distribution; d) granular, contains neoplastic epithelial cells which contain a granular cytoplasm; e) basal which might be similar to basocellular carcinoma of columnar type organized in lawyers 22.
Unicystic ameloblastoma slowly begins as a destructive lesion of the bone in the center, it tends to spread rather than perforate the bone. It is seldom painful unless it gets infected, there are no signs or symptoms, and probably this is the reason why patients allow the tumor reaches large dimensions, without any treatment and producing facial deformity 8. Malocclusion appear in the mandible, abnormal tooth mobility, tooth loss, root resorption, paresthesia in some cases and periodontal disease.
Conventional radiography, CT (Computed Tomography) scan and MRI (Magnetic Resonance Imaging) are useful tools for the diagnosis of ameloblastoma. On radiography, a lytic lesion is displayed, which is observed as a radiolucid unilocular image well defined or multilocular radiolucent, like bubbles in the cortical expansion, finding that image associated with any retained tooth and dental root resorption 3,8,16.
On the Computed tomography it can be appreciated a non-homogeneous mass with cystic areas uni or multiloculated of low-density, and isodense solid regions.
Solid areas may have enhancement with contrast medium, in this image it is shown in a defined manner the lesion extension towards soft tissues 16. On magnetic resonance, the ameloblastoma is presented as a mixed lesion. In the sequence T1 signal intensity is intermediate, of regular walls. In T2, the cystic component has a high intensity, while the solid component is enhanced with the paramagnetic contrast agent, presenting an intermediate intensity 16.
We must consider the patient's age, location and characteristics, both clinical and radiological, so the differential diagnosis is limited to three categories: odontogenic tumors, cystic lesions and benign non odontogenic lesions. Among odontogenic tumors, the Pindborg tumor should be rejected (in its radiolucent variety), odontogenic myxoma and regarding cystic lesions we must take into account the dentigerous cyst and the odontogenic keratocyst or residual cyst. Finally we will consider non-odontogenic lesions, which are: central giant cell granuloma, ossifying fibroma, central hemangioma and, idiopathic histiocytosis.
According to Philipsen Reicha23, factors to be considered when choosing the treatment for ameloblastoma are:
Gold ranks excision procedures of bone lesions. The first one is the conservative, which consists of curettage and enucleation. When performing the enucleation, the lesion is separated from the bone, preserving the continuity of it, in order to leave the lesion circumscribed or encapsulated in an envelope of conjunctive tissue. Curettage is the removal of the bone lesion preserving the bone continuity is performed by scratching due to lack of a capsule or the tissue friability24. The second procedure is the radical. It consists of recession, which is the excision of the lesion, including healthy tissue. In the mandible it is called segmental resection, if continuity is lost of the basal edge or marginal if it does not occur. When tumor is recurrent whether it is intramural or solid, they must be treated by radical resection10.
Male patient, 14 years old, transferred to Hospital del Niño DIF (Child Hospital) by his family health center, presenting a bulging right-sided hemifacial mass, displaying noticeable facial asymmetry, the patient reported paresthesia when right inferior alveolar nerve. Patient reported paresthesia in the right inferior dental nerve. Physical examination shows enlargement of right hemifacial focused on lower third facial region, slightly crackling in posterior areas. Intraorally, it presents a volume growth in region body and mandibular branch with absence of teeth second and third molar of the same side, slight displacement of the first molar, and the presence of deciduous teeth with extensive carious processes (figure 1).
Figure 1. This is the frontal photography of patient’s admission to the Pediatric Dentistry Service.
Initially it was valued an orthopantomography where is observed at the level of mandible right body-branch, radiolucent are with a well-defined edge, covering the right mandibular first molar until ipsilateral condylar region, in the total mandibular thickness from alveolar process to its basal edge, presenting inside the lesion the tooth organs: second and third molar. Third molar is visibly shifted to the region of the right coronoid apophysis (Figure 2).
Figure 2: Patient’s Orthopantomography
The CT scan shows a well-circumscribed hypodense image covering regions described above, appreciating in the axial cut and three-dimensional reconstruction, the buccal and lingual cortical expansion, without drilling data of them, preservation of the basal edge and mandibular condyle (Figures 3 and 4).
Figure 3. Three-dimensional reconstruction (Rear View)
Figure 4. Axial cut of mandible body
It is decided to start the protocol of the clinical case’s study performing a biopsy by aspiration with a fine needle (BAAF).
Obtaining a sample of 3cc of amber liquid which is sent to histopathology, at the same time it is decided to perform, under local anesthesia, incisional biopsy which is diagnosed as cystic ameloblastomas (Figure 5)
Figure 5. Intraoral view of the patient's lesion.
Treatment is then performed under general anesthesia, intubation, surrounding incision with anterior vertical discharge, lesion's exposure in the right hemi-mandible, and then enucleation of it with peripheral osteotomy preserving whole basal mandibular edge, which did not allow placing any type of osteosynthesis. It is designed marsupialization of the gingival tissue when repositioning the flap with absorbable suture, marsupialization of the gingival tissue is designed at the moment of repositioning the flap with absorbable suture, obtaining a clean surgical site with subsequent placement of organdil strips impregnated with nitrofurazone ointment therein.
For patient's treatment, it was decided to change daily the surgical dressing. After two weeks it was found the reepithelialization of the bone cavity and subsequent evolution. Using this technique, a diminution of the bone imperfection occurred until its involution during a period of approximately 6 months in bone healing (figure 6).
Figure 6. This is a postoperative radiography after 6 months of the surgery.
The unicystic ameloblastomas has not preference for any gender 9,13. The most common ages in which this lesion is present goes from a range 20 to 30 years of age13. This lesion can be present in pediatric patients as presented in this clinical case. The most common area where it is presented is the mandible particularly in the region of third molar, and mandible branch 3,9,14,15 which coincided with our clinical case, where the presentation of the tumor was in the right mandibular body. Etiology and factors that trigger this lesion are still unknown, but studies claim that they derive from the epithelium involved with the formation of teeth 3,8,14,19 which can occur, since in our medical case the second and third molar were in formation. Several reports agree on the recurrence and tendency to metastasize. Nakamura et al.25 analyzed 78 cases, in which there was found a 7.1% recurrence for radical treatment and 33.3% for conservative treatment. Sehdev et al.26 with 92 cases, reported a recurrence rate of 90% when treated by curettage
Muller and Slootweg 27 study 84 cases, they report a recurrence rate of 52% in patients treated with conservative treatment and a recurrence rate of 25% in patients treated with radical treatment. In this case it was chosen a conservative treatment, since a radical treatment mutilates pediatric patients (due to young age), which reduces the growth capacity and jaws development 28. Due to the high rate of recurrence with conservative treatment, it was decided to keep under observation for about six months, obtaining bone defect reduction until its bone scar involution. There is a risk of recurrence of the tumor in the first year after conservative treatment, for that reason observation should be kept during one year and give to it follow up for 5 years.
It is a big challenge to choose the best therapeutic for ameloblastoma treatment, since high recurrence, however, it is important to take into account: the patient's age, size and location. In this clinical case it was chosen a conservative treatment, despite the high rate of recurrence. The follow up of the patient is realized. Excellent results have been obtained without any tumor recurrence.
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 Hospital del Niño DIF Hidalgo, Pachuca, Hidalgo. Mexico.