Jordi | Journal of Oral Diagnosis Online Submission Review an Article SOBEP - Sociedade Brasileira de Estomatologia e Patologia Oral
Volume 2 - 2017

Review Article

DOI: 10.5935/2525-5711.20170044

Global frequency of benign and malignant odontogenic tumors according to the 2005 WHO classification

Leorik Pereira da Silva1; Rômulo Augusto de Paiva Macedo1; Marianna Sampaio Serpa2; Ana Paula Veras Sobral3; Lélia Batista de Souza1

1. Federal University of Rio Grande do Norte, Natal-RN, Brazil
2. A.C. Camargo Cancer Center, São Paulo-SP, Brazil
3. University of Pernambuco, Camaragibe-PE, Brazil

Corresponding authors: Rômulo Augusto de Paiva Macedo

Article received on April 22, 2017.
Article accepted on August 27, 2017.



Odontogenic tumors are a heterogeneous group of lesions with variable clinical behavior. This manuscript aimed to determine the global frequency and distribution of OT based on the 2005 WHO classification. The manuscript performed a systematic search conducted in only one database (PubMed/Medline). We identified 8,658 articles, of which 495 articles were evaluated. After applying the inclusion and exclusion criteria, 42 papers were selected. Summed up, a total of 13,490 cases of OT were diagnosed. Most cases were found in Asia (n=6,472) and North America (n=2,599). Keratocystic odontogenic tumor (KCOT) (32.1%) was the most frequent neoplasm, followed by ameloblastoma (AMB) (30.6%) and odontoma (ODO) (17.3%). Malignant tumors were uncommon, accounting for 4.7% of all tumors. Of those, malignant ameloblastoma (n=184) and ameloblastic carcinoma (n=115) were the most common tumors. Overall, OT were more prevalent in men (n=4,896), with a male:female ratio of 1.2:1. The age ranged from 1 to 92 years; however most tumors occurred between the second and fourth decades of life. The mandible was the most common anatomical site, with a mandible:maxilla ratio of 2.8:1. The prevalence profile of OT shows a geographical variation; moreover, studies based on prior WHO classifications present a different incidence and frequency. The 2005 WHO classification of OT altered the distribution of these lesions and possibly made KCOT the most common OT observed worldwide.

Keywords: Odontogenic Tumors; Epidemiology; Jaw Neoplasms.



Odontogenic tumors (OT) consist of several lesions derived from tooth-forming apparatus presenting various histological, cytological, and architectural patterns. They range from hamartomatous lesions to true neoplasms (benign or malignant), exhibiting distinct clinical behaviors1-3. In order to better comprehend these lesions, facilitate communication between physicians and improve treatment, the World Health Organization (WHO) developed a classification system for OT in 1971. The edition (2005) highlights their histological types and biological behaviors, by dividing them in groups4.Some re-organizations made along the WHO classifications result in great divergences between authors. The inclusion of KCOT and CCOT as OT, formerly considered cysts, is one of the most controversial discussions. Several papers published after the 2005 WHO classification maintains considering KCOT and CCOT as cysts, not including them in OT studies5,6. This leads to different epidemiological profiles of cysts and OT3,7,8. However in the WHO classification 2017 reconsidered his position and classified these lesions as odontogenic cysts9. Furthermore, previous studies show the prevalence of OT differs according to the geographical location; nevertheless, the lack of standardization concerning the edition of the WHO classification makes it necessary to better describe the frequency of these tumors. Thus, the objective of this study was to determine the global epidemiology of OT through a systematic search of the literature considering only studies based on the 2005 WHO classification.


A systematic search was conducted in the PubMed/Medline database for papers published from January 2006 to December 2016. Studies that evaluated the incidence and/or frequency of OT following the 2005 WHO classification were selected4 . Entry terms included: "odontogenic tumors", "odontogenic tumours", "odontogenic lesions", "epidemiology" and "WHO classification", using the Boolean operators "AND" and "OR". The selected papers must have met the inclusion criteria described below:

• The paper must be full text and written in English;

• Incidence or frequency of OT must be described;

• 2005 WHO classification of head and neck tumors must be followed;

• Country or city where the study was conducted must be informed.

Case reports, papers that followed the 2005 WHO classification but excluded any type of tumor, and those that described the incidence of only one type of OT were not considered. For the initial selection, two independent evaluators screened titles and abstracts. We initially found 8,658 articles, after a critical analysis of abstracts, 495 articles were selected. Then, the papers judged pertinent were analyzed in their entirety and the 42 studies selected were defined in a consensus meeting and included in the systematization of the data (Figure 1). Information regarding the geographic location, gender, age (categorized in decades of life), anatomical location, and histological type of tumor were recorded.


A total of 42 papers met the established criteria: 15 in Asia, 9 in South America, 9 in Africa, 6 in North America, 2 in Europe and 1 in Oceania (Table 1). They described from 14 to 1,677 cases of OT and summed up, they accounted for 13,490 cases of OT. The majority of the studies was conducted in Asia (n=6,472; 48%) and the minority in Oceania (n=93; 0.7%).

Tumors of odontogenic epithelium, without odontogenic ectomesenchyme

The most frequent tumors in this group were KCOT and AMB. Both occurred more in men, with a male/female ratio of 1.5:1 and 1.2:1, respectively. For the other tumors, women were more affected. Apart from AOT, the mandible was the most common anatomical site (Table 2). The age of the patients ranged from 1 to 87 years and was more prevalent between the 2nd and 4th decades of life (Table 3).

Tumors of odontogenic epithelium with odontogenic ectomesenchyme

ODO was by far the most frequent tumor in this group, occurring more in women, followed by CCOT, which was more common in men. Higher incidence in the mandible was observed, with the exception of ODA (Table 3). The age ranged from 2 to 92 years and was more prevalent between the 1st and 2nd decades of life. CCOT, in particular, was more common between the 2nd and 5th decades (Table 3).

Tumors of mesenchyme and/or odontogenic ectomesenchyme, with or without odontogenic epithelium

The most frequent tumor in this group was MYX. Overall, all tumors occurred more in women and the mandible was the most common location (Table 2). The age ranged from 3 to 83 years, being more prevalent between the 2nd and 3rd decades of life (Table 3).

Malignant odontogenic tumors

Malignant OT represented only 4.3% of all tumors. MAMB was the most common tumor, followed by AMC. All malignant OT affected more men, with a male:female ratio of 1.6:1, and the mandible was the most common anatomical site (Table 1). The age ranged from 7 to 82 years. Despite the wide age distribution, these tumors showed an increased incidence from the 4th decade of life on (Table 4).


OT are relatively uncommon lesions. Due to their various clinical and histological presentations, a better knowledge regarding their frequency is required. Data shows the frequency of OT differs according to the geographical location. Retrospective studies conducted in South America, North America and Europe show an incidence between 2.2% and 5% among all diagnosed oral lesions3,22,29,31. On the other hand, in Africa15 and Asia16,28 studies report a higher frequency, comprising up to 8.9% of all oral lesions.

In the present review, benign OT accounted for the majority of the cases (n=12,904; 95.7%) and malignant OT represented only 4.3% (n=586) of all tumors. Except for studies that only evaluated malignant OT24,37,41,42, the overall incidence of these tumors range from 0 to 5.9%8 7-23,25-36,38-40,43-48, corroborating our data.

Regarding the gender, most OT occurred in men. However, some studies in South America3,12,32, North America17 and Asia20 showed a higher incidence of these tumors in females. The age varied widely throughout the decades of life. In general, a higher prevalence between the 2nd and 4th decades of life was observed, according with other review papers49,50. ODO and AFO were the exception, occurring more in the first and second decades of life. In contrast, malignant OT occurred more in older patients, with a peak incidence from the 4th decade of life on, as also reported by Avelar et al.49 and Johnson et al.50.

Mandible was the main anatomical location with a mandible:maxilla ratio of approximately 2.8:1, similarly to other papers49,50. Nevertheless, the studies performed in Africa19,21,33,34,45 presented a higher mandible:maxilla ratio when compared to studies conducted in other continents, reaching up to 11:1.

KCOT was the most common neoplasm considering all OT. On the other hand, previous studies based on the 1971 and 1992 WHO classification32,49,50, aside from showing a smaller incidence of OT, they reported AMB and ODO as the most frequent tumors. Regardless of whether there is an agreement on the classification of this tumor, the fact is the inclusion of KCOT in the 2005 WHO classification, in addition to increase the overall frequency of OT, also led to a change in the epidemiological profile of these tumors worldwide3,8,17. Nevertheless, we emphasize that the KCOT was removed from the recent WHO classification of odontogenic tumors, it was once again classified as cyst, this fact certainly will lead to a different profile of global incidence from now on9.

In the Asian and African continent, despite the introduction of the tumors (KCOT and CCOT), AMB remains the most frequent tumor1,18,19,21,23,26,28,33,36,38,43-47. Besides that, globally, AMB currently represents the second most common OT diagnosed based on 2005 WHO classification.

The third most prevalent tumor was ODO. The low incidence of these tumors may happen because of underdiagnosed. The indolent behavior, self-limited growth and pathognomonic radiographic appearance lead many surgeons to perform their removal and discard them, not sending samples for histopathological analysis. Still, ODO was the most frequent tumor in some studies conducted in Europe30, North America10, South America13,27, Asia35 and Africa14.

In relation to the malignant OT, MAMB was the most frequent one in our review. This tumor, also named as metastatic AMB, accounted for 31.4% of the malignant OT. Interestedly, North America was the only continent to report MAMB as the most common malignant tumor42. In the other continents, AMC followed by PIOSCC were more frequent. In this review, AMC was the second most common malignant neoplasm, representing 19.6% of all malignant OT. Concerning the diagnosis of MAMB, it may be difficult, as it does not present pleomorphism, necrosis, mitosis and other malignancy characteristics. Except for the ability to emit nodal and/ or distant metastasis, they are morphologically identical to a conventional AMB4. Because of this imprecise clinical and histopathological behavior, the recent WHO classification recategorized MAMB as a benign tumor, naming "Metastasizing (malignant) ameloblastoma"9. We consider this classification controversial, since the ability to emit metastasis is characteristic of cancer.

A single case in this review diagnosed as odontogenic carcinosarcoma was classified as unspecified malignant tumor, since the WHO (2005) excluded this tumor from the classification due to the absence of evidence as a separate entity from other odontogenic carcinomas4,35. However, sclerosing odontogenic carcinoma and odontogenic carcinosarcoma has been added to the recent WHO classification9, although rare, the addition of these tumors will also change the incidence of malignant OT from now on.OT present different incidence profiles according to the geographical location, which became evident in this paper. The five main tumors diagnosed worldwide in descending order were: KCOT, AMB, ODO, MYX and AOT. However some odontogenic tumors are unreported. In addition, the incidence and frequency of these tumors are different when compared to studies based on the WHO classifications prior to 2005. There was a significant change with the addition of KCOT and CCOT in the 2005 WHO classification of head and neck tumors that led to an increase of approximately 35% in the total number of OT diagnosed to date.


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