International Journal of Oral & Maxillofacial Surgery
Volume 39, Issue 9 , Pages 843-846, September 2010

Adenomatoid odontogenic tumour: review of the literature and an analysis of 33 cases from South Africa

  • A. Mohamed

      Affiliations

    • Department of Maxillofacial and Oral Surgery, University of Limpopo, South Africa
    • Corresponding Author InformationAddress: Ashraf Mohamed, Department of Maxillofacial and Oral Surgery, School of Oral Health Sciences, University of Limpopo, PO Box D22, Medunsa 0204, South Africa. Tel.: +27 12 521 4858; fax: +27 12 521 3832.
    • ,
  • A.S. Singh

      Affiliations

    • Department of Maxillofacial and Oral Surgery, University of Limpopo, South Africa
    • ,
  • E.J. Raubenheimer

      Affiliations

    • Department of Oral Pathology, School of Oral Health Sciences, University of Limpopo, South Africa
    • ,
  • M.M.R. Bouckaert

      Affiliations

    • Department of Maxillofacial and Oral Surgery, University of Limpopo, South Africa

Accepted 9 June 2010. published online 20 July 2010.

Article Outline

Abstract 

The adenomatoid odontogenic tumour (AOT) is a benign lesion of odontogenic origin. It is a slow growing tumour that results in a painless expansion of the jaws. This is a retrospective review of the demographic, clinical and radiographic features of AOTs diagnosed in a black South African population over 20 years. Of the 746 odontogenic tumours diagnosed, 4% were AOTs. The patients’ ages ranged from 9 to 37 years with a mean age of 15 years. The highest incidence was in the second decade of life (85%). The female to male ratio was 5.6:1. The maxilla was more commonly affected than the mandible in a ratio of 1.5:1. The sizes of the lesions ranged from 2 to 7cm, with 60% involving an entire quadrant. All were of the central follicular type and appeared as well-demarcated radiolucent lesions. The canine was the most common impacted tooth. The treatment of choice was enucleation of the lesion, with no recurrences being reported.

Keywords: adenomatoid odontogenic tumour, odontogenic tumour, mandible, maxilla, relative frequency, geographic distribution

 

The adenomatoid odontogenic tumour (AOT) is a lesion that is unique to the maxillofacial area with a tendency to affect the deciduous tooth bearing areas of the mandible and maxilla7, 17. It is a slow growing, benign lesion of odontogenic epithelial origin. They are regarded as benign neoplasms by most authors, although some have classified them as harmatomas16, 18.

AOTs have been described since the early 1900s under various names. The literature is inconclusive about who first described the lesion. Steensland19 described the epithelioma adamantinum in 1905, while Dreibladt5 described the pseudoadenoameloblastoma in 1907. In 1915, Harbitz9 reported a cystic adamantoma in a 15-year-old female. The AOT was first regarded as a distinct entity by Stafne in 1948;16 he did not name the tumours, but he described three cases in which the epithelial components formed duct-like structures. Unal et al.21 have reviewed the terminology used to describe the AOT since 1905, which included adenoameloblastoma, adenoameloblastic odontoma, ameloblastic adenomatoid tumour and adenomatoid ameloblastoma.

The name ‘adenomatoid odontogenic tumour’ was first proposed by Philipsen and Birn in 196913, and adopted by the World Health Organization (WHO) Classification of odontogenic tumours in 197110, 20. The WHO4 defines the AOT as ‘a tumour composed of odontogenic epithelium in a variety of histoarchitectural patterns, embedded in a mature connective tissue stroma and characterized by slow but progressive growth’. AOTs have generally been accepted to have a relative frequency of 2–7% of all odontogenic tumours, making them the fourth or fifth most common odontogenic tumours14, 15. A recent multi-centre study has shown the relative frequency of AOT in the African continent, specifically Nigeria, is as high as 39%16.

The age distribution ranges from 3 to 82 years, with 90% being diagnosed before the age of 30 years11, 15, 18. It is more common in females than in males in a ratio of 1.9:1. The maxilla is affected more than the mandible, with the anterior part of the jaw being more frequently involved than the posterior part4, 6, 14. The tumour has been found to arise from the deciduous tooth bearing area of the jaw. An impacted maxillary canine is the most common tooth to be associated with AOT3, 7, 17.

The AOT appears in three clinical variants: a follicular type, an extra-follicular type and a peripheral type. The follicular type occurs intraosseously and is associated with an unerupted tooth. It is often mistaken for a dentigerous cyst because of its radiographic appearance with a well-defined unilocular radiolucency surrounding the crown and often part of the root of an unerupted tooth. The extra-follicular type also occurs within the bone but is not associated with an unerupted tooth. The peripheral type occurs extraossously, and often appears as a fibroma or an epulus on the gingival soft tissues4, 5, 12, 14.

Reports from various parts of the world outline the demographic and clinico-pathologic features of AOT. Most reports on AOT from Africa have come from Nigeria1, 2, 3, 8. There have been no reports detailing the demographic and clinico-pathologic features of AOTs in a South African population. The present study is the first comprehensive study of a series of AOTs from South Africa, and is being reported in keeping with the recommendation by Philipsen et al.16.

The aim of this study is to determine the relative frequency, demographic, clinical and radiographic features of AOT in a South African population, and to compare this data with those from other countries, specifically with studies from Africa.

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Materials and methods 

This was a retrospective review of the demographic, clinical and radiographic features of AOTs diagnosed over a 20-year period from 1986 to 2006. Data collected included age, gender, radiographic site and size of the lesion, associated impacted tooth and treatment. The site of the lesion in the mandible and maxilla was divided into anterior teeth (incisors and canine) and posterior teeth (premolars and molars).

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Results 

From 1986 to 2006, 746 odontogenic tumours were diagnosed; 33 were diagnosed as AOTs (4%). All 33 patients were from a rural and peri-urban black population of the northern part of South Africa. The patients’ ages ranged from 9 to 37 years; the mean age was 15 years. The age distribution is shown in Fig. 1. The highest incidence was found in the second decade of life (28 cases; 85%). All except one case occurred before the age of 30 years. There were 28 females (85%) and 5 males (15%), a ratio of 5.6:1 (Fig. 2).

20 (61%) AOTs occurred in the maxilla and 13 (39%) in the mandible; a ratio of 1.5:1. The site distribution of the AOTs is shown in Fig. 3. In the maxilla, 14 cases (42%) extended from the incisors to the molars (i.e. the entire quadrant was affected). Three cases (9%) affected the incisor–canine–premolar area and 3 (9%) affected the incisor–canine area. In the mandible, 6 cases (18%) extended from the incisors to the molars, and 5 cases (15%) affected the incisor–canine–premolar area. Only 2 cases (6.1%) affected the incisor area of the mandible. Most cases (20/33; 61%) affected an entire quadrant of either jaw. Of the lesions that crossed the midline, 4 were in the maxilla and 7 in the mandible; a total of 11 cases (33%).

The sizes of the lesions ranged from 2 to 7cm with a mean of 4.7cm. All of the AOTs were of the follicular type (i.e. associated with an impacted tooth). The most common impaction for both jaws was the canine (22; 67%). The most commonly impacted tooth in the maxilla was the canine (16; 49%) followed by the premolar (3; 9%) and lateral incisor (1; 3%). In the mandible, the canines and premolars were equally affected (6 each; 18%) followed by the lateral incisor (1; 3%). There were no extra-follicular or peripheral AOTs in this series.

All the patients were treated with enucleation of the lesion followed by primary closure. To date there have been no recurrences.

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Discussion 

AOT is an uncommon lesion of odontogenic origin. It is a slow growing tumour that causes a painless expansion of the jaws. A recent worldwide literature survey has found the relative frequency of AOTs to be much higher than the 2–7% cited by Philipsen et al.15. According to this survey the relative frequency varies from 1% to 39%16. If the distribution of AOTs is analysed according to the geographic location, the relative frequency of AOTs in the different parts of the world is: Europe: 1–4%; Middle East: 2–4%; North America: 2–7%; South America: 4–7%; Asia: 1–16%; and Africa: 1–39%. Philipsen et al.16 give several reasons for this large range especially on the African continent. Firstly, the diagnosis of an AOT should be standardized according to the WHO4 classification of odontogenic tumours; secondly, the reclassification of the odontogenic keratocyst to the keratocystic odontogenic tumour may significantly influence the overall number of odontogenic tumours and hence the relative frequency; and thirdly, the concept of a ‘harvesting phenomenon’ where untreated tumours accumulate due to lack of treatment facilities giving the false impression of the prevalence of these tumours. They also suggested standardizing the age range for paediatric patients. In the present study, AOTs constituted 4% of all odontogenic tumours, a range well within those in the various parts of the world.

Most patients were in the second decade of life (85%), with all except one presenting before the age of 30 years (Fig. 1). This is in accordance with previous reports3, 4, 6, 8, 11, 12, 16. The global female to male ratio is 1.9:114, 15. The gender distribution varies depending on the geographic region. For non-Asians, the female to male ratio is 1.4:1; for Asians 2.3:115 and for African countries 2.5:11. In the current study, females were affected more than males in the ratio of 5.6:1 (85%). This ratio is much higher than those previously reported, and much higher than those reported from Nigeria1, 2, 3. As this is the first comprehensive study from a South African population, it may indicate a further regional variation in gender distribution.

A striking feature of this series is that all the cases were of the central type and all were of the follicular type (associated with an impacted tooth). There were no peripheral AOTs. The maxilla was affected in 61% of the cases (1.5:1), with the most common impacted tooth being the canine (80%). In the mandible, the canine and premolars were equally affected (46%). The above findings are consistent with the literature. Philipsen et al.16 in their multi-centre study and Aritoba et al.3 in a study in Nigeria found the maxilla to be more commonly affected in a ratio of 1.8:1.

None of the cases in this series involved impacted deciduous teeth or impacted permanent molars. None of the cases arose in areas not preceded by deciduous teeth (i.e. incisor, canine, premolar area). This finding supports the theory that AOT arises from the epithelial rests of Mallassez at the apex of deciduous teeth7, 17.

Radiographically, the lesions appeared as well-demarcated unilocular radiolucencies associated with an unerupted tooth. There were no radiopacities noted within the radiolucency. Philipsen and Reichart14 reported that approximately two-thirds of the intrabony cases have scattered radiopacities within the radiolucency. It has also been found that intra-oral radiographs rather than panoramic radiographs are best suited for showing up the discrete calcified deposits16.

A unique feature of this South African population is the large size of the AOTs. 61% of the cases affected an entire quadrant. Two of the cases included in this series were previously reported on by Raubenheimer et al.17. They noted the large size of the lesions, and attributed this to a higher growth rate in younger patients and a delay in seeking treatment. The patients in the current series come from disadvantaged socio-economic communities, and hospitals are often not accessible. Also many patients visit traditional or tribal healers before seeking conventional medical treatment. The large size of these lesions supports the classification of AOT as a benign neoplasm and not a harmatoma. By definition, a neoplasm has an unlimited growth potential, whereas harmatomas have a limited growth potential and differentiate into more mature tissue with time17.

This is the first report from South Africa describing the demographic and clinico-pathologic features of AOT. This series is unique to other series, including those from Africa, in that all were of the follicular type. There were no peripheral AOTs. The incidence in females was much higher than that reported in the world literature, with a female to male ratio of 5.6:1. Most lesions (61%) involved an entire quadrant of either the maxilla or the mandible. None were associated with an impacted permanent molar tooth or a deciduous tooth. It may be that within different geographical locations there are further regional variations in the presentation of the AOT.

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Competing interests 

None declared.

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Funding 

None.

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Ethical approval 

Approval obtained from the Medunsa Research and Ethics Committee (MREC). Research number DP06/07.

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References 

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PII: S0901-5027(10)00295-X

doi:10.1016/j.ijom.2010.06.014

International Journal of Oral & Maxillofacial Surgery
Volume 39, Issue 9 , Pages 843-846, September 2010

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