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

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 7 cm, 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.

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 maxilla . 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 harmatomas .

AOTs have been described since the early 1900s under various names. The literature is inconclusive about who first described the lesion. S teensland described the epithelioma adamantinum in 1905, while D reibladt described the pseudoadenoameloblastoma in 1907. In 1915, H arbitz reported a cystic adamantoma in a 15-year-old female. The AOT was first regarded as a distinct entity by S tafne in 1948; he did not name the tumours, but he described three cases in which the epithelial components formed duct-like structures. U nal et al. 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 P hilipsen and B irn in 1969 , and adopted by the World Health Organization (WHO) Classification of odontogenic tumours in 1971 . The WHO 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 tumours . A recent multi-centre study has shown the relative frequency of AOT in the African continent, specifically Nigeria, is as high as 39% .

The age distribution ranges from 3 to 82 years, with 90% being diagnosed before the age of 30 years . 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 part . 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 AOT .

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 tissues .

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 Nigeria . 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 P hilipsen et al. .

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.

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).

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 ).

Fig. 1
Distribution of AOT according to age groups.

Fig. 2
Distribution of AOT according to gender.

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%).

Fig. 3
Distribution of AOT according to anatomical site.

The sizes of the lesions ranged from 2 to 7 cm with a mean of 4.7 cm. 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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Feb 8, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Adenomatoid odontogenic tumour: review of the literature and an analysis of 33 cases from South Africa
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