|Year : 2014 | Volume
| Issue : 2 | Page : 145-151
Prevalence of ameloblastoma: A three-year retrospective study
Ramesh Tatapudi, Shaik Abdul Samad, Reddy Sudhakara Reddy, Naveen Kumar Boddu
Department of Oral Medicine and Radiology, Vishnu Dental College, Bhimavaram, Andhra Pradesh, India
|Date of Submission||24-Jun-2014|
|Date of Acceptance||15-Sep-2014|
|Date of Web Publication||30-Oct-2014|
Department of Oral Medicine and Radiology, Vishnu Dental College, Vishnupur, Kovvada, Bhimavaram - 534 202, West Godavari, Andhra Pradesh
Source of Support: Outpatient department, Vishnu dental college, Conflict of Interest: None
| Abstract|| |
Context: This study intends to assess the data on the prevalence and types of ameloblastoma reported in the Outpatient Department retrospectively, so that the distribution of ameloblastomas among this geographic area can be reported. Aims: To retrospectively analyze and evaluate the distribution and frequency of ameloblastoma cases based on the gender and histopathological types. Settings and Design: Retrospective study. Materials and Methods: Radiographs and biopsy records of all histologically diagnosed cases of ameloblastoma archived from January 2010 to December 2012 were retrieved from the Outpatient Department. Statistical Analysis: Descriptive statistics were performed to calculate the frequency and percentages of these variables. Age was stratified into various groups at 15-year intervals. The chi-square test for differences between two groups and the analysis of variance (ANOVA) test for differences among three or more groups were used. The level of statistical significance was set at P < 0.05. Results: From the data of ameloblastoma patients, about 30 cases were short-listed and their data was analyzed. It was found that the 15-30 year old age group had the highest percentage of occurrence (about 46.6%) among all cases. Frequently the posterior segment and vertical ramus of the mandible was involved. Radiographically, unilocular appearance was noted in 50% of the cases and unicystic ameloblastoma was the most frequently encountered histological subtype (49.9%). Conclusion: Studies on the incidence of ameloblastoma among the Indian population is rare. By performing a meta-analysis at the level of societies and geographic places, we can identify the demographic distribution of common odontogenic lesions like ameloblastoma among the various populations.
Keywords: Ameloblastoma, Indian, plexiform, retrospective, unicystic
|How to cite this article:|
Tatapudi R, Samad SA, Reddy RS, Boddu NK. Prevalence of ameloblastoma: A three-year retrospective study
. J Indian Acad Oral Med Radiol 2014;26:145-51
|How to cite this URL:|
Tatapudi R, Samad SA, Reddy RS, Boddu NK. Prevalence of ameloblastoma: A three-year retrospective study
. J Indian Acad Oral Med Radiol [serial online] 2014 [cited 2019 Mar 24];26:145-51. Available from: http://www.jiaomr.in/text.asp?2014/26/2/145/143687
| Introduction|| |
Ameloblastoma is an odontogenic tumor arising from the epithelial rests of Malassez, occurring mostly in the mandible  and the tumor arises from the epithelium that plays a role in the process of tooth development.  A marked geographic variation is apparent in the relative incidences of various odontogenic tumors, particularly ameloblastoma. ,,,
Robinson defined Ameloblastoma as, "Usually unicentric, non-functional, intermittent in growth, anatomically benign, and clinically persistent". In most cases, an ameloblastoma is usually asymptomatic, grows slowly, and can expand jaws.  Microscopically, ameloblastoma is composed of epithelial islands in collagen connective tissue stroma.  The ameloblastoma also has a few variations in histopathological appearance, but the most common types are follicular and plexiform.  However, the trigger for neoplastic transformation of the epithelium has remained unknown.  Besides its invasive characteristic, the ameloblastoma also has a tendency to recur, therefore, this tumor is usually considered as a localized malignant tumor.  Ameloblastoma is relatively not sensitive to radiotherapy, therefore, resection surgery or hemisection are the choices of treatment.  The percentage of ameloblastoma occurrence among males and females has been reported with varied opinions in literature. Many studies have been published on the distribution of the ameloblastoma describing its demographic parameters, and there have been several case series on ameloblastomas from several countries, with geographical and/or racial variations.
The objective of this study was to retrospectively analyze and evaluate the distribution and frequency of ameloblastoma cases based on the histopathological types and gender, from January 2010 to December 2012, at the Outpatient Department of Oral Medicine and Radiology, Vishnu Dental College, Bhimavaram, West Godavari District, Andhra Pradesh. An attempt was made to correlate our findings with similar reports in literature. This would enhance the understanding of the prevalence and occurrence of this unique tumor limited to the odontogenic apparatus, thereby enabling us to treat them effectively.
| Materials and Methods|| |
The case records and surgical biopsy reports of all diagnosed cases of ameloblastoma archived from January 2010 to December 2012 were retrieved from the Outpatient Department of Oral Medicine and Radiology, Vishnu Dental College, Bhimavaram, West Godavari District, Andhra Pradesh. A retrospective study of 30 cases of ameloblastoma was done, extracting parameters such as age, sex, location, radiographic findings, histopathological appearances, treatment, and recurrence from the records and comparing them with other reported studies.
For analysis of the mandibular ameloblastomas, the site of occurrence was categorized into anterior (incisal-canine), body (premolar-molar region), posterior (distal to third molar), and bilateral regions (across the midline). For the mandible, the posterior area also included the ramus, angle, coronoid process, and condyle. For the maxillary tumors, the site was subdivided into anterior (incisal-canine) and posterior (distal to canine) regions. Any tumor involving two or more sites was assigned to the region approximating the center of the lesion. Any recurrent tumors arising from these cases were not considered as separate or additional cases. Sections of all primary and recurrent tumors stained with hematoxylin and eosin were retrieved and reviewed to classify them according to the criteria of the recent World Health Organization (WHO) classification of odontogenic tumors. 
Descriptive statistics were performed to calculate the frequency and percentages of these variables. Age was stratified into various groups at 15-year intervals. The chi-square test for differences between the two groups and the Analysis of Variance (ANOVA) test for differences among three or more groups was used. The level of statistical significance was set at P < 0.05.
| Results|| |
Over the three-year study period, 30 histologically confirmed ameloblastomas were analyzed. The distribution of these cases according to ethnicity, anatomic location, radiologic appearance, and clinicopathological subtypes are presented here. The statistical analysis showed significant differences in the distribution of ameloblastomas in relation to their radiographic and histopathological appearance (P < 0.05).
In the present study, the data showed the following age and sex distribution of ameloblastomas. Out of 30 patients, 14 (46.6%) cases occurred in the 15-30 year old age group, followed by seven (23.3%) in the 31-45 year old age group, and seven (23.3%) cases in the 45-60 year old age group [Figure 1]a. Among 30 patients, 18 (60%) patients were males and 12 (40%) patients were females [Figure 1]b.
|Figure 1: (a) Age distribution of ameloblastomas and (b) Sex distribution of ameloblastomas|
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In the 18 males, six (19.9%) ameloblastomas occurred in the mandibular body region and in the 12 females there were seven (23.3%) [Table 1]. There were five cases (16.6%) of ameloblastomas seen in the maxillary posterior region in males and one case in females (3.3%). The number of ameloblastomas seen in the mandibular posterior region in males were two (6.6%) and in females three (10%). There were three (10%) ameloblastomas seen in males in the bilateral regions (crossing the midline). The number of ameloblastomas seen in the mandibular anterior region in males was one (3.35%) and in females was also one (3.35%). There was one (3.3%) ameloblastoma seen in maxillary anterior region in males [Figure 2].
The radiographs of the 30 cases were evaluated. Out of the 30 cases, unilocular radiolucency was seen in 15 (50%) cases (ten males (33.3%) and five females (16.6%)), multilocular radiolucency was seen in nine (30%) cases (four males (13.3%) and five females(16.6%)), and mixed radiopacity and radiolucency was seen in six (20%) cases (four males (13.3%) and two females(6.6%)). The results are summarized in [Table 2] and [Figure 3].
The various histological subtypes of ameloblastoma are listed in [Table 3] and [Figure 4]. Among the histopathological types, the intramural variant was the most commonly occurring (in nine (30%) cases, of which five were males (16.6%) and four were females (13.3%)), followed by the plexiform type, accounting for six (20%) cases, of which three (10%) were males and three (10%) were females. The unicystic type accounted for five (16.6%) cases, of which three (9.96%) were males and two (6.64%) were females. The desmoplastic variant was seen in three (10%) of the cases, of which two (6.6%) were males and one (3.3%) was female. The follicular variant was seen in three (10%) males, acanthomatous and intraluminal variants were seen in one (3.3%) male each, and plexiform and follicular variants were seen in one (3.3%) female each. There was no occurrence of a granular or basal cell histopathological type of ameloblastoma. Statistical analysis showed significant differences in the distribution of ameloblastomas, in relation to their radiographic and histopathological appearance (P < 0.05), which is statistically significant.
|Figure 4: Distribution of various histological subtypes of ameloblastomas|
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| Discussion|| |
Ameloblastomas are an enigmatic group of oral tumors. They are usually benign in growth pattern, but frequently invade locally and occasionally metastasize. They have a persistent and slow growth, spreading into the marrow spaces with pseudopods, without concomitant resorption of the trabecular bone. As a result, the margins of the tumor are not clearly evident radiographically or grossly during operation, and consequently, the lesion frequently recurs after inadequate surgical removal, demonstrating a locally malignant pattern. 
Age of occurrence
In the present study, out of 30 patients, 14 (43.3%) cases occurred in the 15-30 year old age group. From the data of 30 cases obtained from the surgical biopsy records of all the histologically diagnosed cases of ameloblastoma that were retrieved from the files of the Outpatient Department, in the period from January 2010-December 2012, it was found that the age group with the highest number of ameloblastoma cases was the 15-30 year old group with 14 cases (43%), followed by the 31-45 year old group with seven cases (23.3%), then by the 45-60 year old group with seven cases (23.3%), and finally the above 60-year-old group with two cases (23.3%). The result of this study corresponded with the analysis of Small and Waldron (1955) and Mehlisch, Dahlin, and Masson (1972), of 1036 cases, which asserted that ameloblastoma cases occurred most frequently in 20-50 year old patients, with almost half of the number in the third and fourth decades of life. 
The average age of presentation that has been reported in literature is between 30 and 33 years.  The peak incidence in Asia fell in the third decade of life, as compared to the fifth decade of life in North America. The explanation for this difference may reflect the ethnic and possibly socioeconomic differences, as almost all of the patients from Asia are of Asian descent, whereas, in North America most are Whites. In addition, people in North America frequently have better access to medical care than people in developing countries, such as Thailand and Vietnam. North American patients are more likely to have regular dental visits and routine radiographic check-ups. As a consequence, oral lesions are detected at a younger age. The explanation for the lower average age of patients with ameloblastoma in developing countries compared with that of industrialized countries may reflect poor nutrition and reduced access to the healthcare system in developing countries, as proposed by Dodge's concept, which may not be entirely applicable. Korea, for example, is an industrialized country with a high standard of living and a well-respected healthcare system, but has an average age of patients with ameloblastoma comparable with that of other Asian countries. In all countries, the age of patients with unicystic ameloblastoma is lower than that of patients with solid/multicystic ameloblastoma. This is in accordance with the previous studies. The present study reveals an almost equal gender distribution, which is also in accordance with the previous studies, with the exception of selective studies that demonstrate either male or female predominance. 
Site of occurrence
It is well-recognized that ameloblastomas occur more frequently in the mandible than in the maxilla, and are located predominantly in the body and posterior mandible. In the present study, more than 50% of the ameloblastomas have been found in the mandible and most of these tumors have also been located in the body and posterior regions. There is a consensus in the literature that ameloblastomas more frequently affect the mandible, primarily in its posterior region.  Gardner has reported that about 80% of the ameloblastoma tumors occur in the mandible; and of the other 20%, most occur in the posterior part of the maxilla, with only a few occurring in the anterior maxilla. Our report further shows that 60% of the cases occurred in the posterior (molar-premolar) region of the mandible and 6.7% in the anterior mandibular segment. About 20% of cases were located in the posterior segments of the maxilla, with only 3.3% located in the anterior segment, and 10% crossed the midline. This distribution in the maxilla is in agreement with the report of Gardner. 
In most cases, the ameloblastoma presents with a characteristic, although not diagnostic, radiographic appearance.  Radiographically, the margins of the lesion in the mandible are usually well-defined, frequently corticated, and occasionally scalloped. In contrast, in the maxilla, the margins are severely ill-defined as the lesion tends to grow along the bone rather than expanding it. The internal structure varies from totally radiolucent to mixed, with the presence of bony septa creating internal compartments. The compartments in the bone are round and of varying size. The septae are usually coarse and curved, and originate from the normal bone that has been trapped within the tumor. With growth or expansion of the tumor, there may be coalescence and fusion of the compartments, and as a result, there may be transformation from a multilocular to a monolocular cystic space. Tumors in which the compartments are large and few in number may resemble a multilocular epithelium-lined cyst. 
The radiographic appearance of ameloblastoma is variable. H.M. Worth has described four patterns  [Figure 5] and [Figure 6]a-d:
|Figure 5: Schematic diagram showing radiographic appearance of ameloblastomas|
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|Figure 6: (a) A cropped panoramic radiograph showing a unicystic type of ameloblastoma, (b) a mandibular occlusal radiograph showing the spider-web type, (c) a cropped panoramic radiograph showing the soap-bubble type, and (d) an intraoral periapical radiograph showing the honeycomb type|
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- Unicystic type: This appears as a unilocular radiolucency resembling a cyst. However, unlike a cyst, it causes a break or discontinuity in the peripheral cortex and may even show trabeculae within the lumen.
- Spider-web pattern: This is the most common appearance, where the lesion is seen as a large radiolucent area with scalloped borders. From the center of the lumen coarse strands of trabeculae radiate peripherally, giving rise to a gross caricature of a spider.
- Soap-bubble pattern: This lesion is seen as a multilocular radiolucency with large compartments of varying sizes, giving rise to the soap-bubble appearance or a multi-chambered or multicystic 'bunch of grapes' appearance.
- Honeycomb or solid pattern: This is also called a beehive pattern. These are tumors that have not undergone cystic degeneration. Hence, multiple small radiolucencies are seen surrounded by hexagonal or polygonal thick-walled bony cortices, giving rise to a honeycomb appearance.
In the present study, the number of patients presenting with unilocular appearance (50%) was comparable with that of patients with multilocular radiolucencies (30%). This is in accordance with the review conducted by Reichart and co-workers, but conflicting data still exist from other studies. Kim and Jang conducted a study in Korea and reported that almost 60% of the cases were composed of unilocular ameloblastomas, while approximately 20% were multilocular.  Some studies revealed that multilocular radiolucencies outnumbered unilocular radiolucencies, whereas, the contrary was true for others.  On analysis of the average age of appearances of unilocular and multilocular ameloblastomas, statistically significant results were obtained. It can thus be inferred that the unilocular variety occurred at a younger age in comparison to the multilocular variety.
In this study, among the histopathological types, the unicystic ameloblastoma was the most frequently encountered histological subtype (49.9%), followed by plexiform (20%), follicular (10%), and hemorrhagic and acanthomatous types (3.3%). There was no occurrence of the granular or basal cell histopathological type of ameloblastoma.
The results are in accordance with Rajeshwar Chawla et al. study in 2013, which showed that unicystic ameloblastoma was the most frequently encountered histological subtype (34%), followed by follicular (19.8%), plexiform (22%), granular cell (9.9%), and acanthomatous type (6.6%) ameloblastomas. Our results are different from Reichart and Philipsen's study (1995), which showed that follicular ameloblastoma was the most frequently encountered histological subtype (33.9%), followed by plexiform (30.2%), acanthomatous (11.3%), and unicystic (6%) type ameloblastoma.
Ameloblastomas are unique tumors with a strong tendency to recur after treatment. Recurrence in ameloblastoma is believed to be the result of several risk factors, notably tumor subtype, treatment method, and tumor behavior. Tumors with a follicular, granular, or acanthomatous growth pattern have a reportedly high likelihood of recurrence, whereas, desmoplastic, plexiform, and unicystic subtyes have a relatively low recurrence potential. 
There are no randomized trials of solid/multicystic ameloblastoma with regard to the type of surgical treatment. The suggested treatments vary from simple enucleation and marsupialization followed by resection or curettage, to aggressive removal, including the margin of a one-tissue plane in the soft tissues, when cortical perforation is present, clinically or radiographically. Nevertheless, a debate on the preferred treatment is ongoing.
From the reports on ameloblastomas, it seems acceptable to group the treatment regimens into three modalities:
- Conservative (includes enucleation and curettage),
- Marsupialization, and.
- Radical surgery (includes resection with or without the continuity defect). 
In case of a preoperative diagnosis of solid/multicystic ameloblastoma in children, it is tempting, mainly for psychosocial reasons, to perform less aggressive surgery.  Furthermore, some authors have suggested that ameloblastomas in children may behave less aggressively. At the same time, one may advocate not to be less aggressive in view of the high recurrence rate after conservative surgery and the long-life expectancy at childhood.
In case of a unicystic ameloblastoma, based on an incisional biopsy, some authors recommend decompression followed by enucleation within three to four months.  However, a preoperative biopsy in unicystic ameloblastoma is not always representative;  in fact, Ackerman, et al. recommends that incisional biopsy not be performed in these circumstances.  In the past, unicystic ameloblastomas have been reported to behave less aggressively than the solid/multicystic type. However, in several recent studies this view has been challenged.
Little is known about the role of postoperative radiotherapy in case of incomplete removal. There is no reliable data on the possible value of additional treatment modalities, such as, the use of liquid nitrogen or tissue fixatives such as Carnoy's solution, although such practice is recommended by some authors. 
In a large series reported from South Korea, the follicular, granular cell, and acanthomatous types had a relatively high likelihood of recurrence, while the desmoplastic, plexiform, and unicystic types showed a relatively low potential for recurrence.  However, in the meta-analysis from Pogrel and Montes the histopathological subtypes, including unicystic ameloblastomas, did not seem to be relevant in this respect.  Partly based on our own experience, and also based on a number of large studies performed by others, the chance of recurrence seemed to be more dependent on the method of surgical treatment rather than on the histological subtype. 
In general, an annual follow-up for at least 10 years is recommended. Others recommend annual follow-up until five years and every two years thereafter, for at least 25 years. For the mandible, the use of a panoramic view seems adequate. Unfortunately, the panoramic view is not very suitable for the detection of a possible recurrence in the maxilla or the maxillary sinus. In fact, in this location computed tomography (CT) scans are by far superior. To eliminate ionizing radiation exposure, magnetic resonance imaging (MRI) may be an ever better imaging tool for maxillary lesions. 
On the basis of the experiences reported in literature, a treatment protocol has been proposed in [Table 4].  Among the therapy modalities, surgery is still the therapy of choice. In this study, almost all cases have been primarily treated with surgery. 
| Conclusion|| |
The objective of reporting ameloblastomas in this geographic area has been fulfilled. Even though the sample size has been small, the data, including a three-year, long-term, follow-up is useful for assessment of improving the different treatment modalities. As studies on the incidence of ameloblastomas among the Indian population are rare, by performing similar studies in different geographic areas in our country, as a meta-analysis, at different levels of societies and geographic places, we can have a demographic distribution of common odontogenic lesions similar to ameloblastomas among the Indian population.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4]