Ninety-one cases of ameloblastoma in an Indian population: A comprehensive review.

AIM: To assess the cases of ameloblastoma retrospectively for various parameters.
MATERIALS AND METHODS: Ninety-one previously reported cases of ameloblastoma from Government Dental College and Hospitals, Nagpur, were included in this study. Data were collected considering parameters such as age, sex, symptoms, radiographic, histopathology, treatment modalities, and recurrence. Our findings were also compared with world literature.
RESULTS: The average age was 32.5 years. Mostly men complained of an asymptomatic swelling and duration of less than one year. Posterior segment and vertical ramus of mandible was the frequently involved site. Radiographically, multilocular appearance was noted more than 60% of the cases. Plexiform and unicystic ameloblastoma occurred frequently. Surgery was the treatment of choice in this review. Recurrence was noted in more than 10% of the cases.
CONCLUSION: There are variations in our review in comparison to reported literature.

INTRODUCTION

Odontogenic tumor has been a topic of considerable interest to oral pathologists who have studied and catalogued them for decades. This constitutes a group of heterogeneous lesions that range from hamartomatous or non-neoplastic tissue proliferation to malignant neoplasm with metastatic capacity.[1] A marked geographic variation is apparent in the relative incidences of various odontogenic tumors, particularly ameloblastoma.[2345] Ameloblastoma was the most common tumor in studies done on Chinese,[67] Japanese, and African populations,[89] while in American and Canadian populations, the most frequent tumor was odontome.[1011]

On the basis of World Health Organization (WHO) classification, a retrospective study was undertaken of ameloblastoma in the central region of India, Nagpur city (Vidharbha region). An attempt was made to correlate our findings with similar reports in literature. This would enhance the understanding of prevalence and occurrence of this unique tumor limited to the odontogenic apparatus, thereby enabling us to treat them effectively.[12]

MATERIALS AND METHODS

One hundred ninety-nine cases of odontogenic tumors were retrieved from files of Department of Oral Pathology and Microbiology, Government Dental College and Hospitals, Nagpur, from 1977 to 2003. A retrospective study of 91 cases of ameloblastoma was done considering parameters such as age, sex, location, duration, radiographic findings, and histopathological appearances and these were compared with other reported studies. The data were analyzed with unpaired t-test, Chi-square goodness-of-fit test, Analysis of variance (ANOVA) tests for statistical significance.

OBSERVATIONS AND RESULTS

Out of 7,700 surgical specimens received in the department, 199 were diagnosed as odontogenic tumors. This accounts for 2.5% incidence. Out of these, 91 cases were diagnosed as ameloblastoma, thus accounting for 45.7% of odontogenic tumors and 1.18% of surgical specimens [Figure 1].

Figure 1

Percentage of occurrence of various odontogenic tumors

The age at the time of presentation was in the range of 10-60 years, with a median at 30 years. The peak incidence occurred in the third and fifth decades. Average age was 32.5 years [Figure 2]. Out of the 91 patients, 49 (53.8%) were male and 42 (46.2%) were female. The male:female ratio was 1.2:1 [Figure 3]. When the age was analyzed separately for male and female patients, the mean age of males and females was 31 and 34.2 years, respectively [Figure 4]. Two-tailed, unpaired student t-test was applied and a value of P > 0.2543 was found. Hence, the difference in the average age of males and females was non-significant.

Figure 2

Age distribution of ameloblastoma

Figure 3

Sex distribution of ameloblastoma

Figure 4

Age distribution of ameloblastoma in male and female patients

Out of 91 patients, 55 (60.4%) reported with asymptomatic hard swelling. Pain followed by swelling (n = 32, 35.2%), ulceration (n = 9, 9.9%), mobility of teeth (n = 10, 11%), displaced teeth (n = 4, 4.4%), and paresthesia (n = 5, 5.5%). The mean, median, and mode duration of symptoms are 16.4, 6, and 12 months, respectively [Table 1].

Table 1

Duration of symptoms amoug ameloblastoma

The clinical history was non-contributory in seven cases. About 51.6% of patients presented to the hospital within 11 months of symptoms and 22% reported within 2 years [Figure 5].

Figure 5

Duration of symptoms before clinical presentation of ameloblastoma

The site distribution of various ameloblastomas among males and females is listed in Table 2. The ratio of ameloblastoma occurring on the right side as compared to the left was 0.83:1. The highest incidence of ameloblastoma (46%) was seen in the posterior segment and vertical ramus of the mandible [Figure 6].

Table 2

Site distribution of ameloblastoma in males and females

Figure 6

Site distribution of ameloblastoma in male and female patients

The various histological subtypes of ameloblastoma are listed in Table 3 and Figure 7. Unicystic ameloblastoma was the most common type with an incidence of 34.1% (n = 31), followed by plexiform ameloblastoma (22%, n = 20) and follicular ameloblastoma (19.8%, n = 18). The sex distribution [Table 4], age distribution [Table 5 and Figure 8], and site distrib ution [Table 6] were also assessed.

Table 3

Histological variants of ameloblastoma

Figure 7

Distribution of various histological subtypes of ameloblastoma

Table 4

Sex distribution of various ameloblastoma

Table 5

Age distribution of various ameloblastoma

Figure 8

Age distribution of different variants of ameloblastoma

Table 6

Site distribution of various of ameloblastoma

Radiographs of 85 cases were evaluated [Table 7]. Unilocular appearance was observed in 29 (34.1%) cases, while multilocular appearances were observed in 56 (65.9%) cases. Other radiographic findings included embedded tooth (n = 7), root resorption (n = 12), missing tooth (n = 5), and egg shell crackling (n = 3). The most common embedded tooth was the third molar. The average age of 25.3 years was seen in the unilocular variety as compared to multilocular appearances at an average age of 34.8 years.

Table 7

Radiographical assessment of ameloblastoma

The management of ameloblastoma could be traced for 71 cases and is summarized in Table 8, as 20 patients were not willing for treatment. Curettage and enucleation was performed in 21 cases, marginal resection in 7 cases, while segmental resection was done in 43 cases. Out of 43 cases, 23 were followed by reconstruction.

Table 8

Management of ameloblastoma

Follow-up was done in 46 cases and recurrence was noted in 9 cases, accounting for 14.1% cases [Figure 9]. Radical treatment was given for all recurrent cases. Recurrence developed at average time interval of 7.4 years, median was 7 years, and the maximum was 15 years. On recurrence, follicular variant was noted in four cases and unicystic ameloblastoma was found in five cases. Out of these, two were plexiform unicystic type, one of follicular unicystic type, and one of unicystic ameloblastoma with granular cell metaplasia. Granular cell ameloblastoma was noted in one case on recurrence.

Figure 9

Various periods of recurrence

DISCUSSION

The most frequent tumor in this review was ameloblastoma, with an incidence of 45.7% comparable to that found by Lu et al. (58.6%)[6] and Wu et al. (59.4%)[7] among Chinese population. This finding contrasts with rates in series involving American and Canadian population in whom Ameloblastoma accounted for 12.2% and 14.8%, respectively.[13]

The average age of the patient at the time of initial diagnosis was 32.5 years, which is similar to that in the Chinese population in whom tumors were presented at the mean age of 32.4 years.[7] Reichart and Philipsen in their biological profile of 3,677 cases found the average age of 35.9 years at the time of initial diagnosis.[14]

Female patients reporting with tumor had a mean age of 34.2 years, which was higher than that of male patients with a mean age of 31 years. In our series, 53.8% of the patients were was men and 46.2% were women comparable to Reichart and philipsen study[14] in which 53% were male and 47% were female.

There is striking predilection for the mandible though maxillary lesion varies considerably among the reports. In the present series, a single case of tumor occurred in the maxillary region, a figure not comparable to corresponding data of Asian/African countries (2-8%) and American series (16-22%).[8]

The predilection of ameloblastoma for the posterior segment is 25.3% and posterior segment and vertical ramus is 40.6%, which is consistent with reports elsewhere.[151617181920]

Our review revealed a multilocular appearance (60.4%) and unilocular appearance (31.9%), which was higher than that of Reichart and Philipsen's study,[14] in which multilocular appearance was noted in 49% and unilocular in 51% cases. Statistically significant results were obtained when average age of unilocular and multilocular appearances was analyzed, indicating that unilocular occurred in younger age group as compared to multilocular ameloblastoma.

In our review, unicystic ameloblastoma was the most frequently encountered histological subtype (34%) followed by follicular (19.8%), plexiform (22%), granular cell ameloblastoma (9.9%), and acanthomatous type (6.6%). Our results are different from Reichart and Philipsen's study (1995),[11] which showed follicular (33.9%) plexiform (30.2%) acanthomatous (11.3%) and unicystic (6%) types.

When different variants of ameloblastoma were analyzed separately for males and females, the results were non-significant in all variants of ameloblastoma. Hence, no particular sex distribution was seen in different variants of ameloblastoma.

When average ages of different variants of ameloblastoma were analyzed statistically using the ANOVA test, it was found that plexiform ameloblastoma occurred in younger age group as compared to follicular, acanthomatous, and granular cell ameloblastoma.

It is evident from our review that unicystic and plexiform variants occurred at a younger age and more frequently involved the body and ramus area of the mandible. In contrast, the acanthomatous type occurred in older patients and involved the anterior segment of jaws. Granular cell type and desmoplastic type occurred in older patients and were seen involving both anterior and posterior segments of mandible.

Among the therapy modalities, surgery is still the therapy of choice.[21] In this study, almost all cases were treated primarily with surgery.

Follow-up was done in 46 patients, with a recurrence of 14.1%, which is less than the Reichart and Philipsen's study (22.6%).[14] On recurrence, The follicular variant (four cases), unicystic type (five cases), and granular type (one case) are not consistent with Reichart and Philipsen's study, which reported follicular (29.5%), plexiform (16.7%), and unicystic types (13.7%).[11] The decrease in recurrence rate in the last few decades could be attributed to early diagnosis and improved therapeutic approach.[102223]

The study on incidence of ameloblastoma among Indian population is rare. There is only one excellent review of 73 cases of ameloblastoma by Krishnapillai R and Angadi PV.[24] Our review adds valuable information on the incidence of ameloblastoma in Indian population to the existing limited literature. Our study was performed over a period of 26 years (1977-2003). Out of 7,700 cases received in the department, odontogenic tumors comprise 2.5%. This is lower than the reported incidence of 2.97% by Osterne et al.[25]

CONCLUSION

It must be stressed that our knowledge of biological behavior of ameloblastoma is still insufficient for drawing a definite conclusion. Many more detailed reports including long-term follow-ups are needed for proper assessment of treatment modalities.