Elsevier

Oral Oncology

Volume 35, Issue 2, March 1999, Pages 125-131
Oral Oncology

Review
Adenomatoid odontogenic tumour: facts and figures

https://doi.org/10.1016/S1368-8375(98)00111-0Get rights and content

Abstract

The present profile of the adenomatoid odontogenic tumour represents an update based on data collected from 1991 onwards. Our present knowledge discloses the AOT being a benign (hamartomatous), slow growing lesion which occurs in several intraosseous (follicular (F) and extrafollicular (EF)) and one peripheral variant all having identical histology. The F and EF variants account for 96 per cent of all AOT's of which 71 per cent are F variants alone. F and EF variants together are more commonly found in the maxilla than in the mandible with a ratio of 2.1:1. Age distribution shows that more than two thirds are diagnosed in the second decade of life and more than half of the cases occur within the teens (13–19 years of age). The female:male ratio for all age groups and AOT variants together is 1.9:1. The marked female predominance (around 3:1) among certain Asian poplulations needs further clarification. The distribution of unerupted permanent teeth found in association with the F variant shows that all four canines account for 59 per cent and the maxillary canines alone for 40 per cent. Recent findings strongly indicate the AOT is derived from the complex system of dental laminae or its remnants. Occurence of areas of CEOT-like tissue in an otherwise “classic” AOT should be considered a normal feature within the continous histomorphological spectrum of AOT. Immunohistochemical and ultrastructural findings have revealed that the eosinophilic deposits or “tumour-droplets” most probably represent some form of enamel matrix.

Section snippets

Terminology and classification

The tumour that meets today's diagnostic criteria of an adenomatoid odontogenic tumour (AOT) has been known for more than 90 years. We agree with Unal et al.[1]that Steensland's report from 1905 of an “epithelioma adamantinum” represents the earliest publication of an AOT for which sufficient documentation is available. A variety of terms have been used to describe this lesion of which the adeno-ameloblastoma was in common use for many years since the tumour was considered a histological

Histological definition

In the recent 2nd edition of the WHO “Histological Typing of Odontogenic Tumours”[7]the AOT has been defined as:

A tumour of odontogenic epithelium with duct-like structures and with varying degrees of inductive change in the connective tissue. The tumour may be partly cystic, and in some cases the solid lesion may be present only as masses in the wall of a large cyst. It is generally believed that the lesion is not a neoplasm

.

Clinical and radiographic definitions

The AOT is a benign (hamartomatous), non-invasive lesion with a slow but progressive growth. It occurs in intraosseous as well as in peripheral forms (Fig. 1). Radiographically, the intrabony variants comprise a follicular and an extrafollicular type.

The follicular type shows a well-defined, unilocular (round or ovoid) radiolucency associated with the crown and often part of the root of an unerupted tooth thus mimicking a dentigerous or follicular cyst. In fact, 77% of follicular type AOT are

Relative frequency

Information on incidence and prevalence of individual odontogenic tumours is still not available. Surveys of oral pathology biopsy services from various sources do, however, provide information about relative tumour frequencies. Table 1 gives the relative frequency of the AOT extracted from 12 oral biopsy surveys9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19. Thus, it has been estimated that the AOT accounts for between 2.2 and 7.1% of all odontogenic tumours which gives this tumour a ranking of

Pathogenesis

The fact that all AOT variants show identical histology strongly points towards a common origin and most authors agree on an odontogenic source. Based on present knowledge of the biology of the AOT, Philipsen et al.[5], have strongly argued in favour of the concept of AOT being derived from the complex system of dental laminae or its remnants. Until more is known about the fate of the numerous epithelial remnants persisting in the jaw bones and gingiva after completion of odontogenesis, we are

Macroscopic

The intrabony AOT variants are roughly spherical in shape with a well-defined fibrous capsule. The cut surface may reveal a solid tumour mass or show one large or several small cystic spaces containing a yellowish, semi-solid material. In the follicular type a crown and often part of the root of an unerupted tooth is found embedded in the tumour mass or projecting into a cystic cavity. Estimation of the total protein level in aspirated fluid from cystic spaces in two intrabony AOTs[5]revealed a

Treatment

Since all variants of AOT show an identical, benign biological behaviour and since they in almost all reported cases are well encapsulated, conservative surgical enucleation or curettage has proven the treatment modality of choice. In only three (all Japanese) among 750 cases has recurrence of this tumour occurred[40]and in only one instance was extension of recurred tumour into the intracranial space recorded.

Acknowledgements

The authors are indebted to Dr Mosqueda-Taylor and co-workers for supplying detailed data of the 25 AOTs included in their publication[19].

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