Odontogenic tumours: 240 cases diagnosed over 31years at a Brazilian university and a review of international literature


This study describes the epidemiology and clinical presentation of odontogenic tumours (OT) seen at a regional Brazilian oral and maxillofacial pathology service; to assess the quantitative impact of the most recent World Health Organization (WHO) classification of these lesions; and to compare this series with others available in international databases. The study was carried out by retrospectively analysing 240 cases diagnosed from 1978 to 2009, followed by a comprehensive review of the literature. The patients’ mean age was 29 years, with a male to female ratio of 1:1.1. Benign lesions comprised 97.9% of the cases (mostly keratocystic odontogenic tumours (KCOT), odontomas and ameloblastomas) with the remaining tumours depicting a prevalence of less than 5%. Adenomatoid OT were less frequent than in most previous studies, while malignant OT were strikingly numerous. Most OT in children and in the anterior maxilla were odontomas, while maxillary ameloblastomas were rare. Lack of swelling was more frequent in KCOT than in ameloblastomas. The present study confirms the relative impact of KCOT in the epidemiology of OT and identifies more similarities between the present series with reports from the United States and Europe than with African and Asian populations.

Odontogenic tumours (OT) constitute a heterogeneous group of lesions derived from the tooth-forming apparatus. They include hamartomatous lesions, benign neoplasms with varied biologic behaviour and malignant tumours. These lesions are uncommon, some are extremely rare, and can pose significant challenges in the diagnostic and therapeutic care of the patients. Knowledge of their epidemiology and clinical presentation is essential, and retrospective studies have been carried out in Africa, Asia, North America, South America and Europe to describe these lesions.

Recently, the World Health Organization (WHO) introduced conceptual changes in the OT chapter of the current classification of head and neck tumours, which has been considered the most substantive among the eight parts of the volume. The epidemiological impact of these changes has been investigated in only a few comparative studies.

The present study seeks to describe the demographic and clinicopathologic presentation of OT in the oral and maxillofacial pathology service of a Brazilian federal university, to evaluate the impact of the new classification on the relative frequency of these lesions, and to compare this series with others published in the English language and available in international bibliographical databases.

Materials and methods

This cross-sectional, retrospective study was approved by the local Institutional Committee for Ethics on Research. The files of an oral pathology service from 1978 to 2009 were revised to select all the cases with a diagnosis of OT tumours according to the recent WHO Classification of Head and Neck Tumors. This revision was jointly performed by three of the authors, all of whom have more than a decade of experience in the diagnosis of OT. The medical and dental files of each patient, including their radiographic images, were evaluated for age, gender, and race as well as evolution, location, and extent of the lesions. Regarding the anatomic distribution of the lesions, three regions were considered for the maxilla: anterior (between the distal surface of the canines); premolar (from the mesial surface of the first premolar to the distal of the second premolar); and posterior (from the mesial surface of the first molar further distally). The mandible was divided into five anatomic regions: anterior, premolar, molar, angle, and ramus.

Those lesions involving two or more areas were assigned to the region closest to the centre of the lesion. Data were summarized and analysed with GraphPad Prism statistical software, version 5.0. The Mann–Whitney test was used to compare means of quantitative variables, with χ 2 or Fisher’s exact test to verify possible associations between categorical variables, with critical level of significance stated at p < 0.05.

A literature search was performed with the online electronic databases PubMed, Medline, LILACS, and Cochrane reviews for English language publications between 1971 and 2010. Search terms used were ‘odontogenic tumors’ and ‘epidemiologic study’. A manual search was also made for cross-references from the initially retrieved papers. Case reports, series on specific lesions, or studies limited by age or anatomic site were excluded, except for two sequential papers from the same centre on peripheral and central OT, which were taken together. El-Gehani, Wu, and Daley included other lesions in their papers but gave OT in separated tables and, therefore, were included. For each study, the authors collected the referential WHO classification, year range, country, sample size, relative frequency of OT, patient demographics, and main clinical features. Studies that did not mention the WHO classifications or did not strictly follow these classifications were adapted to the more similar classification. When appropriate, χ 2 or Fisher’s exact tests were employed to verify associations between categorical variables, or the Mann–Whitney test was performed to compare mean values between two groups. Probability values less than 5% were considered significant.


From 11,181 examinations of oral and maxillofacial lesions, 334 (3.0%) were initially diagnosed as an entity then known as OT or as a lesion presently recognized as such, corresponding to 240 patients ( Table 1 ). All were kept as initially diagnosed after histopathologic review; changes were only attributable to conceptual adjustment to the contemporary WHO reference. The classification of keratocystic odontogenic tumour (KCOT) as an OT increased the proportion of these lesions by 50.9% (from 159 to 240 cases), and was responsible for the highest quantitative impact. The proportion of benign to malignant lesions was 47:1. Taken together, KCOT, odontoma, and ameloblastoma corresponded to nearly 85% of the cases. The other tumours comprised less than 5% of the series. Table 2 presents the demographic data. Females were slightly predominant. Fewer than 5% of the patients were under 10 years old, more than half were diagnosed in the second and third decades, and nearly 10% were diagnosed in persons aged 60 years and older. Sex and age distribution do not change whether or not KCOT had been considered. For children and teenagers, odontoma was the prevalent tumour, with decreasing frequency until the sixth decade. KCOT and then ameloblastoma were the most frequent aggressive lesions observed in teenage to elderly patients, with decreasing frequency from young adults. Malignant tumours were restricted to adults and presented at higher average age ( p = 0.04, Mann–Whitney test) and evolution time ( p > 0.05) than benign lesions. The proportion between non-African and African ancestry patients was similar in both benign and malignant groups (2:1 versus 3:1).

Table 1
Frequency of odontogenic tumours by histological type seen at the oral and maxillofacial pathology service of a Brazilian federal university (1978–2009).
Histological type N %
Benign tumours 235 97.9%
Odontogenic epithelium with mature fibrous stroma and without odontogenic ectomesenchyme 129 53.8%
Ameloblastoma (AME) 48 20.0%
Calcifying epithelial odontogenic tumour (CEOT) 2 0.8%
Adenomatoid odontogenic tumour (AOT) 3 1.3%
Keratocystic odontogenic tumour (KCOT) 76 31.7%
Odontogenic epithelium with odontogenic ectomesenchyme, with or without hard tissue formation 86 35.8%
Odontoma (OD), compound type (OD Cp) 34 14.2%
OD, complex type (OD Cx) 42 17.5%
Calcifying cystic odontogenic tumour (CCOT) 9 3.8%
Dentinogenic ghost cell tumour (DGCT) 1 0.4%
Mesenchyme and/or odontogenic ectomesenchyme, with or without odontogenic epithelium 20 8.3%
Odontogenic fibroma (OF) 5 2.1%
Odontogenic myxoma/myxofibroma (OM) 11 4.6%
Cementoblastoma (CB) 4 1.7%
Malignant tumours 5 2.1%
Odontogenic carcinomas 5 2.1%
Ameloblastic carcinoma, primary type (A Ca, p) 3 1.3%
Primary intraosseous squamous cell carcinoma, solid type (PIO SCCa, S) 1 0.4%
Clear cell odontogenic carcinoma (CCO Ca) 1 0.4%
Odontogenic sarcomas 0%
Total 240 100%

Table 2
Sex and age distribution of the present 240 odontogenic tumours according to histological type.
Histological type Sex ratio (M:F) Age (years-old)
0–9 10–19 20–29 30–39 40–49 50–59 60–69 70–79 NA Mean (SD) Range
Benign 1:1.1 3% 37% 18% 11% 12% 5% 3% 4% 6% 28 (17.7) 3–87
KCOT 1:0.8 28% 18% 11% 16% 9% 7% 4% 8% 34 (18.2) 10–87
OD 1:1.4 9% 53% 17% 8% 7% 3% 4% 19 (12.2) 3–58
AME 1:1.0 29% 15% 17% 17% 2% 2% 13% 6% 36 (20.6) 11–83
OM 1:4.0 55% 18% 9% 18% 21 (6.1) 15–32
CCOT 1:0.5 11% 44% 11% 22% 11% 29 (20.8) 3–65
OF 1:0.7 80% 20% 26 (5.4) 20–34
CTB 1:3.0 25% 25% 50% 39 (19.3) 15–55
AOT 1:2.0 33% 33% 33% 30 (17.8) 14–49
CEOT 1:1.0 50% 50% 31 (13.4) 21–40
DGCT 0:1 100% 39 (−) 39
Malignant 1:0.7 40% 20% 40% 42 (14.7) 27–58
A Ca, p 1:2.0 33% 67% 46 (16.8) 27–58
PIO SCCa, S 1:0 100% 45 45
CCO Ca 1:0 100% 27 27
Total 1:1.1 3% 36% 18% 11% 13% 6% 3% 4% 6% 29 (17.7) 3–87
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Jan 24, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Odontogenic tumours: 240 cases diagnosed over 31years at a Brazilian university and a review of international literature
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