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Table of Contents
Year : 2023  |  Volume : 28  |  Issue : 1  |  Page : 67-72

Adenomatoid odontogenic tumors: Rare cases in Enugu, Eastern Nigeria

Department of Oral Pathology and Oral Medicine, Faculty of Dentistry, University of Nigeria, Enugu State, Nigeria

Date of Submission25-Mar-2022
Date of Decision25-May-2022
Date of Acceptance27-Jul-2022
Date of Web Publication13-Dec-2022

Correspondence Address:
Mark C Nwoga
Department of Oral Pathology and Oral Medicine, Faculty of Dentistry, University of Nigeria, Enugu State
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmh.IJMH_32_22

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Adenomatoid odontogenic tumors (AOTs) are very rare. We present a case series of eight AOTs seen and managed at University of Nigeria Teaching Hospital (UNTH), Ituku-Ozalla, Enugu State, Nigeria over a 10-year period, from 2012 to 2021. Their epidemiological data and clinic-pathological information were obtained from the biopsy forms, histopathology reports, and case files archived in the Records Department of the hospital. The AOTs were diagnosed in 8 patients out of the 225 odontogenic tumors seen during the period giving a prevalence of 3.6%. Five patients (62.5%) were males, whereas three (37.5%) were females giving a male-to-female ratio of 1.7:1. The mean (SD) age at onset of lesion was 12.4 (5.4) years with a range of 5–21 years. The location of the tumors was anterior in 62.5% of the jaw cases. A maxillary location was observed in 62.5% of the cases. Pain complaint was reported in 25% of the subjects. Tumor fluid was aspirated in 75.0% (n = 6) of the lesions: straw aspirate (83.3%),and dark-brown aspirate (16.7%). A tooth was associated with the tumor in 87.5% (n = 7) of the cases, with the canine impacted in 85.7% (n = 6) of these. Only one case (12.5%) was extrafollicular. The AOTs are uncommon and differed from other Nigerian studies by exhibiting a male gender prevalence, lower mean age, and frequent straw aspirates.

Keywords: Adenomatoid, canine impaction, odontogenic tumor, straw aspirate

How to cite this article:
Nwoga MC. Adenomatoid odontogenic tumors: Rare cases in Enugu, Eastern Nigeria. Int J Med Health Dev 2023;28:67-72

How to cite this URL:
Nwoga MC. Adenomatoid odontogenic tumors: Rare cases in Enugu, Eastern Nigeria. Int J Med Health Dev [serial online] 2023 [cited 2023 Feb 8];28:67-72. Available from: https://www.ijmhdev.com/text.asp?2023/28/1/67/363249

  Introduction Top

Adenomatoid odontogenic tumor (AOT) is a benign, slow-growing epithelial tumor of the jaws.[1] It is a rare tumor which arises from remnants of dental lamina.[2] It is reported to constitute 2.2–13% of all odontogenic tumors.[3],[4],[5] However, in Nigeria, it is reported to make up to 4.5% of all odontogenic tumors.[6] AOT occurs most frequently in the second decade of life.[1],[6]

“Two-third tumor” is a term that highlights its characteristic features of constituting two-thirds of cases in four aspects: the maxilla, in young females, in association with an un-erupted tooth, and of canine involvement.[7],[8],[9] A female preponderance has been reported,[1] but a large Nigerian study reported a near equal gender distribution with a male: female ratio of 1:1.3.[6]

AOT presents clinically as intraosseous and extraosseous (or peripheral) types. The intraosseous type is subclassified as follicular and extrafollicular variants depending on the presence or absence of tooth involvement, respectively.[2],[6],[10],[11] The maxilla continues to be the most common site of occurrence.[12] AOT responds well to treatment by enucleation, and the likelihood of a recurrence is very low.[6]

To the best knowledge of the author, no study has reported the prevalence and histopathologic features of AOT among the population of the Southeast Nigeria consisting of native Igbos, one of the three major tribes of Nigeria. The large study of AOTs among Nigerians by Adisa et al.[6] had no data representation from the population of the Southeast Nigerians. This study would also add to the baseline data of AOT cases in Enugu State, Southeast Nigeria.

This is a case series study of the prevalence and clinicopathologic features of AOTs in a tertiary hospital in Enugu, southeast Nigeria.

  Materials and Methods Top

Ethical approval for this study was obtained from the Ethics Committee of University of Nigeria Teaching Hospital (UNTH), Ituku-Ozalla, Enugu (UNTH/CSA/329/OL.5: NHREC/05/01/2008B-FWA00002458-1RB00002323). All the guidelines outlined in the Declaration of Helsinki were met. The study population consisted of consecutive patients in a tertiary hospital who presented at the Oral and Maxillofacial Surgery Clinic and were diagnosed with AOT by histology. This is a retrospective case series covering a period of 10 years (2012–2021). Eligibility for inclusion is the histologic diagnosis of AOT. The exclusion criteria include absence of a diagnosis of AOT and patients with AOT but with incomplete biodata information of age, gender, and site.

Their biodata and clinicopathologic information were extracted from the biopsy forms, histopathology reports, and case files archived in the Records Department. The clinicopathologic information obtained included gender, site of tumor, age at presentation, duration, type of tumor fluid aspirate (straw, dark-brown, and negative aspirates), complaint of pain, radiographic features, histologic type, and treatment modality.

The relevant data on AOT were collected and analyzed using SPSS for Windows (version 20.0; SPSS Inc., Chicago, IL, USA). Descriptive analysis of the data was carried out, and calculations of proportions, frequencies, and percentages and mean and SD were done.

  Results Top

AOT was diagnosed in 8 patients out of the 225 odontogenic tumors seen during the study period giving a prevalence of 3.6%. The gender distribution was 62.5% (5) male and 37.5% (3) female with a male-to-female ratio of 1.7:1. The mean age at onset of lesion was 12.4 (5.4) years, with a range of 5–21 years. The mean duration of tumor before presentation was 20.1 (27.2) months with a range of 2–84 months.

[Table 1] shows the relevant clinical summary of the eight cases of AOTs including age, gender, site, history of pain, and aspirate types. [Table 2] shows a summary indicating that the majority of the lesions, 62.5% (5), occurred on the anterior part of the jaws, whereas the maxilla was the commonest site of these cases. Pain was not a frequent symptom associated with AOTs and was found only in 25% (2) of the lesions. There was no association of gender and pain with AOT [P = 0.67 (confidence interval, CI): 95%]. There was also no significant association between the site of tumor occurrence and history of pain [P = 0.41 (CI: 95%)].
Table 1: Clinical summary of eight cases of adenomatoid odontogenic tumor (AOT)

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Table 2: Frequency of adenomatoid odontogenic tumors

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Tumor aspirates as shown in [Table 3] were observed in 75.0% (6) of the lesions, with straw aspirate being the most predominant. There was absence of significant association of the site of lesion with aspirate type [P = 0.44 (CI: 95%)].
Table 3: Association of site of adenomatoid odontogenic tumors with aspirate type

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A tooth was associated with the tumor in 87.5% (7) of the cases, and the canine constituted 85.7% (6) of these. Only one case (12.5%) was extrafollicular. Similarly, 85.7% (6/7) of the lesions involving a tooth were observed to affect a right tooth, with one mandibular lesion involving a left tooth [Table 1].

The histologic diagnoses were made based on the microscopic identification of proliferations of spindle epithelial cells arranged in rossette whorls or nodules and forming duct-like structures in a myxoid stroma [Figure 1]. The duct-like structures were sometimes empty or contained eosinophilic coagulum [Figure 2]. Plexiform tumor patterns were sometimes also identified.
Figure 1: Photomicrograph of adenomatoid odontogenic tumor. Low power view showing duct-like structures were sometimes empty or contained eosinophilic coagulum. H&E, 100×

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Figure 2: Photomicrograph of adenomatoid odontogenic tumor showing proliferations of spindle epithelial cells arranged in rossette whorls or nodules and duct-like structures. H&E, 400×

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All the eight cases were managed by surgical excision and no recurrence has been observed with follow-up ranging from 1 to 10 years depending on the time of treatment.

  Discussion Top

AOT is commonly described as a “two-third tumor” (66.7%) in Western literature.[7],[8],[9] This was due to its two-third prevalences in maxillary site, female gender, unerupted tooth association, and involvement of the canine tooth.[1],[10],[11],[13]

However, AOT in this study exhibited different epidemiological features with reversed gender predominance of higher male frequency (62.5%), higher unerupted tooth involvement (87.5%), and predominant canine frequency (85.7%). Therefore, the “two-third tumor” description is not applicable to the cases in Enugu, Eastern Nigeria. The “two-third tumor” description was also not remarkably obvious in a large study of other Nigerian regions that reported a maxillary involvement in 55.8%, female involvement in 57.4%, impacted teeth involvement in 61.1%, and canine tooth involvement in 57.6%. The “two-third tumor” characteristics were only nearly applicable in this study, regarding maxillary jaw location (62.5%).

Environmental factors may account for the variations in the distributions of AOT in Nigeria regarding site, gender, impactions, and canine involvement. AOT in black South Africans reported features consistent with the “two-third tumor” description.[1] The variations therefore may not be caused by racial factors.

Adisa et al.[6] observed that AOT predominantly occurred in the anterior jaws of Nigerians in 88.6% of the cases, with more incidence in anterior maxilla (55.8%) than in anterior mandible (32.8%). The higher frequency of anterior jaw location of AOT and maxillary preference of occurrence are consistent with other reports in literature.[1],[6],[13],[14] AOT appears to be rare in posterior maxilla in cases from Nigeria. The large Nigerian study of 61 cases did not report any in the posterior maxilla, and observed few cases in the posterior mandible (11.5%).[6] Similarly, this study did not detect any case located in the posterior maxilla. One of the possible explanations is that the canine tooth most commonly associated with the tumor is located on the anterior maxilla.

The higher male gender ratio observed in this study is not unusual in AOTs. A similar finding was reported by other authors in Ibadan, Nigeria and beyond.[11],[15] There is no explanation known to the author for the predominance of either male or female gender distribution of AOTs in various studies. Similarly, the reasons for the preferential anterior location, maxillary preference, and the canine tooth involvement in AOT are unknown to the author.

The cases of AOT in this series were limited to younger patients with nearly all of them aged 18 years and below. Only one case was aged 21 years at AOT onset. This demonstrates the rarity of the lesion above the second decade in Enugu and agrees with reports of the lesion being sparse above 30 years of age.[1],[13 This does not preclude AOT occurrence in the fifth decade as reported by Adisa et al.[6] in other regions of Nigeria and in the eight decade in a Brazilian study.[16]

The mean age of occurrence of cases in this study (12.4 years) is closer to the 15 years reported in a black South African study,[1] lower than the 17 and 20 years from two large Nigerian studies.[6],[17] Another large Brazilian study reported a mean age of 21 years.[16] The reason for the mean age disparity could be due to the use of age-at-tumor onset in this study for a more representative estimation of the mean age of occurrence.

A noteworthy observation is the right-sided occurrence of majority of the lesions in this series involving a tooth. Consequently, 85.7% (6/7) of such lesions affected a right tooth, and only one case involving a left mandibular tooth. A high frequency of right-sided swellings associated with AOTs has been previously reported by Siriwardena et al.[16] The explanation for the predominant right-sided occurrence of AOT may not be related to differential eruption sequence of the jaws but an incidental finding. The relationship of side of occurrence (right/left) with age was reported to be statistically insignificant.[16] It is not obvious whether the tooth impaction stimulates the development of the lesion, or the developed lesion causes the tooth impaction, or both occurrences are unrelated. The relative late eruption of the canine may not be entirely responsible for the lesion as AOT cases arise long before or after the canine eruption. There are controversies over the hamartomatous or neoplastic nature of AOT,[8] although the lesion is not self-limiting as often observed in true hamartomatous lesions.

AOT was associated with fluid aspirates in most of the lesions in this series, and straw fluid aspirate was most commonly observed. AOT is not primarily a cystic lesion; therefore, the accumulation of straw fluid sufficient for aspiration could be explained by the adenomatous features of duct-like spaces lined by columnar or cuboidal epithelium and microcystic areas in the lesion.[2] Straw aspirates are common findings in benign cystic odontogenic lesions such as dentigerous cysts,[18] and it is suggested that straw aspirates from odontogenic tumors could indicate low aggression and low recurrence potential.[19]

A well-defined unilocular radiolucency, presence of radio-opacities, and presence or absence of tooth structures are common features of AOTs in this study. The well-defined unilocularity and tooth-like radio-opacity were reported by Mohamed et al.[1] and Adisa et al.[6] as the most common (57.4%) radiographic feature in their large studies. Similarly, a cyst-like unilocular radiolucency has frequently been described.[13] Other presentations of multilocularity and multiple opacities were also infrequently described.[6]

The imaging features of mandibular AOT in this series suggest that anterior jaw lesions are characteristically well-circumscribed radiolucencies, an observation also reported by More et al.[11] The well-circumscribed imaging features were probably due to the slower resorption of the mandibular compact bone. The frequent haziness and hyperopacification in maxillary lesions were probably due to radiographic superimpositions and the impacted teeth in most of the cases in this study.

The rate of canine involvement in AOTs could be up to 60%[20] in a recent study among Nigerians, which observed that impacted tooth was associated with the tumor in 61.1% of the cases and these impactions involved the upper canine in 57.6% of the lesions.[6] The present study observed a higher canine involvement of 85.7% in Enugu; this concurs with other reports of the canine being well recognized as the most frequently involved tooth.[1],[21] The higher canine involvement in this series could be due to the small sample and only a single case of the extrafollicular variant in contrast to the 32.8% reported in other regions of Nigeria by Adisa et al.[6]

The rare involvement of a lateral incisor in this series reflects the reported rare involvement of other teeth (lateral incisor, premolar tooth, molars, and deciduous teeth) in follicular AOT. Lateral incisor involvement was similarly reported by More et al.,[11] while Suhas et al.[22] reported the involvement of a premolar tooth in the tumor.

AOT is an important differential of dentigerous cyst. Although dentigerous cyst is typically associated with the cervical portion of a tooth and only related to the crown, AOT behaves in an opposite manner by enveloping both crown and roots. Furthermore, while dentigerous cyst typically exhibits a cystic lining, AOT does not.[8]

This study is limited by a few number of cases due to the rarity of the tumor. However, the report of these sparse cases would provide the baseline data for future review studies.

  New Knowledge Added Top

The study has provided the prevalence of AOT and highlighted its male gender predilection in Enugu. This study reports that AOT also yields similar straw fluid aspirates as reported in dentigerous cysts.[18]

  Conclusion Top

AOTs are uncommon and with some features which differed from other Nigerian studies by exhibiting a male gender prevalence, lower mean age, and frequent straw aspirates. AOT should be included in the clinical differential diagnosis of anterior maxillary swellings in children and adolescents, especially if the swelling is associated with an impacted tooth.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]


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