Frequency of odontogenic tumors: a single-center study of 250 cases in Enugu, Nigeria

Abstract

Background and Objectives:

Odontogenic tumors (OTs) constitute a heterogeneous group of lesions with variable clinical and pathological features. This study aimed to determine the frequency of OTs in the Nigerian population.

Material and Methods:

A retrospective study of histological results of the OTs diagnosed between 2015 and 2024. The information gathered included the age and sex of the patient, location of the lesion, and histological diagnosis. Data analysis was done using Statistical Package for the Social Sciences version 29 computer program.

Results:

Of the 860 histological reports of patients with oral and maxillofacial lesions, 250 (29.1%) were diagnosed with OTs. The male-to-female ratio was 1:1.1. The patients’ ages at diagnosis ranged from 4 to 88 years (mean age of 32.41 years). The most common benign tumor was ameloblastoma (N = 183, 73.2%), while ameloblastic carcinoma (N = 32, 12.8%) was the most frequently diagnosed malignant tumor

Conclusion:

OTs account for one-third of all orofacial lesions in Nigeria. There is a slight predilection for females and young adults are more affected.

Introduction

Odontogenic tumors (OTs) constitute a heterogeneous group of lesions with variable clinical and pathological features due to differences in the level of interaction between the different tissues and growth patterns^[1,2^]. This group of diseases arises from the abnormal proliferation of tooth-forming tissues or their remnants and may, therefore, be derived from tissues originating from epithelium, mesenchyme, or both^[3–6^].

Various studies on this topic have shed more light on the epidemiology of OTs, with distribution ranging from 1% to 28% across different parts of the world, even though most of these works were based on older World Health Organization (WHO) classifications^[1,2,7–9^].

The OTs can be classified as benign or malignant based on their biological behaviors with the benign being frequently reported^[10,11^]. Most studies on OTs found ameloblastoma to be the most prevalent, especially in Africa and Asia^[12,13^], while odontoma was common in Europe and South America^[14,15^]. Equal distributions of the two types were reported in Japan and Turkey^[16,17^]. Malignant odontogenic tumors (MOTs) are generally rare compared to the benign type, with ameloblastic carcinoma (AC) recorded as the commonest, especially in the African population^[12,13,18^].

HIGHLIGHTS

• The incidence of odontogenic tumors (OTs) in Nigeria is high.

• Females are slightly more affected by the OTs.

• The majority of these lesions are benign tumors affecting predominantly young individuals.

The cause of OTs remains unclear, as a majority appear to arise de novo without any known factor^[2,19^]. Studies suggest that mutation in ameloblastin, KRAS, FHIT, and P53 genes plays a role in the development of OTs^[20^]. In some OTs, especially ameloblastoma, it has been noticed that different expressions of certain genes occur at the genetic levels, with some of the genes over-expressed and others under-expressed when compared with the normal levels^[19^]. Studies have also shown that OTs occur excessively within the maxillofacial region, especially in the mandible and maxilla^[1,2,12,21^].

The WHO classified OTs based on tissue types, with the latest (2022) classification featuring six epithelial, four mesenchymal, and four mixed tumors^[9^]. The 2022 WHO classification is similar to the 2017 edition; however, their key differences are (1) the addition of adenoid ameloblastoma under the benign epithelial OTs, (2) the addition of surgical ciliated cyst to the jaw cysts classification, and (3) improved diagnostic aid by the addition of essential and desired diagnostic criteria for each entity^[11^]. This study aimed to evaluate the number and types of OTs diagnosed at University of Nigeria Teaching Hospital (UNTH) Ituku/Ozalla, Enugu, Nigeria, based on the 2022 WHO classification system, as this information has not been reported previously in Nigeria. The study fulfills the STROCSS 2025 criteria for cross-sectional studies^[22^].

Methods

This was a retrospective study of histopathologic reports of biopsied orofacial lesions archived in Oral and Maxillofacial Surgery Department of the University of Nigeria Teaching Hospital (UNTH) Ituku/Ozalla, Enugu, Nigeria. The inclusion criteria were all histological reports of patients diagnosed with OTs who attended between 2 January 2015 and 31 December 2024. The reports with inconclusive diagnoses, with missing data of interest, or without a final diagnosis were excluded.

The information collected for this study included the age and gender of the patient, the location of the lesion, and the histological diagnosis. If a patient had more than one result, including a pre-surgery incisional biopsy and a post-surgical excision of the tumor, only the postoperative result was taken into consideration. This approach was adopted because the excisional specimen is generally more representative of the tumor in its entirety and is therefore likely to yield a more accurate pathological assessment than the preoperative incisional biopsy.

The collected data were coded and analyzed using Statistical Package for Social Sciences Software (SPSS) for Windows (version 29, Armonk, New York: IBM Corp). The continuous variables were presented in the form of the mean and percentages, while the categorical variables were presented in the form of tables. For descriptive purposes, patients’ age was grouped in the range of 10 years, but for univariate analysis, the participants’ age was grouped into four groups: pediatric (0–17 years), young adults (18–35 years), middle-aged adults (36–59 years), and elderly (60 + years). The tumors were categorized per the 2022 WHO classification of OTs. The tumors were also categorized broadly as benign and malignant.

To assess the relationship between demographic characteristics and the nature of the tumor, either one-way analysis of variance (ANOVA) or chi-square tests were used. The α < 0.05 was selected for statistical significance.

Ethical clearance was obtained from the Health Research Ethics Committee of the xxxxxx, and permission to conduct the study was obtained from the appropriate authorities of the department. A generative AI tool (Grammarly) was used to aid in grammar correction and language enhancement during the manuscript’s preparation.

Results

Age and sex of the patients in relation to the nature of the OTs

In this survey, 860 histological reports of patients with oral and maxillofacial lesions were retrieved. Out of these, 250 (29.1%) reports had a diagnosis of OTs. There were slightly more female (N = 131, 52.4%) patients, and the male-to-female ratio was 1:1.1. The patients’ ages at diagnosis ranged from 4 to 88 years, with a mean age of 32.41 [standard error of the mean (SEM) = 1.09] years. A majority (N = 213, 85.2%) of the tumors were benign. The mean patients’ age for benign odontogenic tumors (BOTs) was 31.40 (SEM = 1.19), and for malignant tumors, it was 38.22 (SEM = 2.62). The most (N = 78, 31.2%) common age of the patients was 20–29 years. There was a statistically significant association between the nature of the tumors and the age of patients (groups and mean age), but not for the sex of the patients (Table 1).

Table 1.

Overall distribution of patients according to age groups, sex, and the nature of the lesions.

Age and sex of the participants	Nature of the lesion		P-value
	Benign (N = 213)	Malignant (N = 37)
Age groups (years)
0–9	2 (100%)	-	< 0.001
10–19	60 (98.4%)	1(1.6%)
20–29	65 (83.3%)	13 (16.7%)
30–39	29 (78.4%)	8 (21.6%)
40–49	28 (90.3%)	3 (9.7%)
50–59	8 (50.0%)	8 (50.0%)
60–69	10 (83.3%)	2 (16.7%)
70–79	7 (77.8%)	2 (22.2%)
80–89	4 (100%)	-
Mean age (SEM)
	31.40 ± 1.19	38.22 ± 2.62	0.027
Sex
Female	112 (85.5%)	19 (14.5%)	0.999
Male	101 (84.9%)	18 (15.1%)

Frequency of different OTs according to WHO 2022 classification

The BOTs were the most common (N = 201, 80.4%) OT followed by the MOTs. Majority of the tumors were ameloblastoma (N = 183, 73.2%) followed by the AC (N = 32, 12.8%), while the odontoma and odontogenic myxoma were least identified (Table 2).

Table 2.

Frequency of occurrence of various odontogenic tumors.

Type of tumor	Number	Frequency
Benign odontogenic tumors: 213 cases (85.2%)
Benign epithelial odontogenic tumors: 201 cases (80.4%)
Ameloblastoma	183	73.2%
Adenomatoid odontogenic tumor	11	4.4%
Calcifying epithelial odontogenic tumor	7	2.8%
Benign mesenchymal odontogenic tumors: 7 cases (2.8%)
Odontogenic fibroma	6	2.4%
Odontogenic myxoma	1	0.4%
Benign mixed epithelial and mesenchymal tumors: 5 cases (2.0%)
Ameloblastic fibroma	4	1.6%
Odontoma	1	0.4%
Malignant odontogenic tumors: 37 cases (14.8%)
Ameloblastic carcinoma	32	12.8%
Clear cell odontogenic carcinoma	5	2.0%

Frequency of OTs by age groups and sex

Table 3 shows the number of tumors according to sex and age groups. Ameloblastoma and AC were frequently diagnosed among young adults, while the adenomatoid odontogenic tumor (AOT) was predominantly diagnosed in pediatric patients. The OTs that were frequently identified in patients above 36 years of age were ameloblastoma, AC, and clear cell odontogenic carcinoma (CCOC). Generally, the majority of OTs were more prevalent in females.

Table 3.

Frequency of occurrence of various odontogenic tumors by age group and sex.

Type of tumor	Age group				Sex
	Ped	YA	MAA	Eld	Male	Female
Ameloblast	35(19.1%)	87(47.5%)	40(21.9%)	21(11.5%)	89(48.6%)	94(51.4%)
AOT	8(72.7%)	3(27.3%)	-	-	5(45.5%)	6(54.5%)
CEOT	1(14.3%)	4(57.1%)	2(28.6%)	-	1(14.3%)	6(85.7%)
OdF	3(50.0%)	3(50.0%)	-	-	3(50.0%)	3(50.0%)
OdM	1(100%)	-	-	-	1(100%)	-
AmF	2(50.0%)	2(50.0%)	-	-	1(25.0%)	3(75.0%)
Odontoma	-	1(100%)	-	-	1(100%)	-
AC	1(3.1%)	19(59.4%)	9(28.1%)	3(9.4%)	15(46.9%)	17(53.1%)
CCOC	-	-	4(80.0%)	1(20.0%)	3(60.0%)	2(40.0%)

AC, ameloblastic carcinoma; Ameloblast, ameloblastoma; AmF, ameloblastic fibroma; AOT, adenomatoid odontogenic tumor; CCOC, clear cell odontogenic carcinoma; CEOT, calcifying epithelial odontogenic tumor; Eld, elderly; MAA, middle-aged adults; OdF, odontogenic fibroma; OdM, odontogenic myxoma; Ped, pediatric; YA, young adults.

Location and site of OTs

Overall majority (N = 221, 88.4%) of OTs (benign and malignant) were in the mandible, and the maxilla-to-mandible ratio of 1:7.6. There was no statistically significant difference in the occurrence of benign and malignant tumors in the maxilla and the mandible (P = 0.871). Except for AOT being prevalent in the maxilla, the rest of all OTs had a higher occurrence in the mandible (Table 4).

Table 4.

Frequency of occurrence of various odontogenic tumors according to the jaw involved.

Type of Tumor	Maxilla	Mandible
Benign odontogenic tumors	25 (11.7%)	188 (88.3%)
Benign epithelial odontogenic tumors	24 (11.9%)	177 (88.1%)
Ameloblastoma	14 (7.7%)	169 (92.3%)
Adenomatoid odontogenic tumor	10 (90.9%)	1 (9.1%)
Calcifying epithelial odontogenic tumor	-	7 (100%)
Benign mesenchymal odontogenic tumors	-	7 (100%)
Odontogenic fibroma	-	6 (100%)
Odontogenic myxoma	-	1 (100%)
Benign mixed epithelial and mesenchymal tumors	1 (20.0%)	4 (80%)
Ameloblastic fibroma	1 (25.0%)	3 (75.0%)
Odontoma	-	1 (100%)
Malignant odontogenic tumors	4 (10.8%)	33 (89.2%)
Ameloblastic carcinoma	3 (9.4%)	29 (90.6%)
Clear cell odontogenic carcinoma	1 (20.0%)	4 (80.0%)

Discussion

OTs are common in the jaw bones and should be high on the list of diagnoses of jaw tumors^[1^]. Several works of literature exist on OTs in Nigeria, mostly single centers and a few multicenter studies^[12,13,23^]. However, none of these studies were based on the latest 2022 WHO classification of OTs; hence, this study evaluated the pattern of OTs diagnosed at the University of Nigeria Teaching Hospital (UNTH) Ituku/Ozalla, Enugu, Nigeria, based on this new classification.

In the present study, OT constitutes 29.1% of all biopsied jaw lesions seen within the study period. This prevalence is far higher than previously reported. A slight female preponderance (1:1.1) in this study aligns with some previous reports^[24,25^], while equal proportions in males and females have been reported in some literature^[14,21,26,27^]. Contrary to previous studies on this topic, several studies, including many from Nigeria, reported a higher male prevalence^[7,9,12–14,28^].

The mean age seen in this study is comparable to the mean age of the OTs series reported by researchers from Asia, the Middle East, and Africa^[4,7,9,12,13^]. However, a few studies have reported a higher mean age^[14,28^]. This finding underscores the fact that OTs occur commonly in the third and fourth decades of life^[4,7,9,12,13,16^].

The age range of the patients at diagnosis seen here is consistent with many studies conducted in Nigeria and elsewhere; Ethiopia (8–80 years) by Kebede et al^[2^], in Japan (3–87 years) by Kokubun et al^[7^], in Nigeria (3–88 years) by Okoh et al^[12^], and in Brazil (5–81 years) by de Medeiros et al^[24^]. It is a fact that OTs occurring in young patients are a result of tooth development during this period. However, since these tumors are generally slow-growing and without symptoms, they are only noticed later in life^[7,29^].

OT can be classified as benign or malignant. More than 85% of the biopsied lesions in this study were BOTs (Table 1). This shows that BOTs are common, as supported by many studies globally^[2,7,9–13^].

The prevalence of the MOTs in this study (7.8%) is higher than previously reported by most authors. Jing et al^[30^] in a study in China found the prevalence of MOTs to be 3.9%, Siriwardena et al^[8^] reported 2% in Sri Lanka, while Kokubun et al^[7^] in a study from Japan reported MOTs to be 0.9%. From Nigeria, Lawal et al^[31^] reported an incidence of 4.1% in Ibadan, and Adebayo et al^[32^] reported a prevalence of 3.4% in Lagos. Conversely, it is lower than 19.6% reported in Ethiopia by Kebede et al^[2^]. These findings underscore that MOTs are generally rare globally.

The mean age of the patients with BOTs in this study is 31.4 years, while that of the MOTs is 38.22 years. The higher mean age among those in the malignant group supports earlier findings that this variant occurs mainly from the fifth decade of life^[33^]. Those within the age range of 20–29 years have the highest prevalence of OTs in this study, closely followed by those within the range of 10–19 years (Table 1). This confirms the findings of previous studies that OTs occur commonly between the second and third decades of life^[7,12,13,16^]. The statistically significant association between the nature (type) of the tumors and the mean age seen in this study buttresses the fact that the majority of the tumors occur at a young age (Table 1).

The recent 2022 WHO Classification of OTs (fifth edition) is not very different from the 2017 classification. The only new addition to the benign epithelial tumors is adenoid ameloblastoma^[5^]. The odontogenic cysts classification that was removed in the third edition (2005) and added back in the 2017 fourth edition maintained its place^[17^]. The 2017 WHO classification of OT moved the odontogenic keratocyst and calcifying odontogenic cysts to the group of odontogenic cysts. This inadvertently reduced the prevalence of OTs globally^[24,33,34^].

Based on the 2022 WHO classification of OTs, benign epithelial OTs (ameloblastoma) were the most common in this study, followed by the MOTs (Table 2). The benign mixed epithelial and mesenchymal tumors (ameloblastic fibroma and odontomas) were the least.

In this current study, ameloblastoma was undisputedly the commonest OTs, accounting for about 86% of the BOTs and 73.2% of the overall OT (Table 2). This is in agreement with previous reports showing that ameloblastoma is the most common OT^[9,13,32^]. The high frequency of ameloblastoma in this study adds to the voice that ameloblastoma is more common in the African populations^[2,4,7,12,13^]. However, some authors have reported contrary findings^[7^].

The prevalence of other OTs apart from ameloblastoma in Africa is generally low. In Nigeria, there are diverse findings on the second most common OT after ameloblastoma. While Aregbesola et al^[13^] reported AOT as the next common OT after ameloblastoma, Okoh et al^[12^] found fibromyxoma as the next common in their study. Elsewhere, a study from Ethiopia^[2^] reported Primary Intra Osseous Squamous Cell Carcinoma (IOSCC) as the next highest occurring OT to ameloblastoma. Unlike in this current study, the prevalence of occurrence of odontoma as the highest OT has been reported in a few studies^[9,11,14,16,17,24^]. These findings give credence to the fact that the prevalence of these tumors varies among countries and races^[2,7^].

This study revealed that ameloblastoma is more common among young adults, followed closely by middle-aged adults and the pediatric group (Table 3). It is rare among those within the elderly group. The findings support the findings of previous work from elsewhere^[4,7,12,13,23,24,35^].

The findings from this study indicate that AOT is the next most common among the pediatric age group (0–19 years), in line with previous Nigerian reports^[12,13^]. However, this contradicts other studies that found calcifying epithelial odontogenic tumor (CEOT), odontogenic fibroma, odontogenic myxoma, ameloblastic fibroma, and odontoma as the next most frequent OTs in the pediatric age group^[2,4,7,21,24^].

Previous studies suggest that MOTs are rare, with a rate of occurrence ranging between 0.2% and 5.7% across different parts of the globe^[7–9,24,32,33,35^]. Although the etiology of MOTs is unknown, they are believed to arise either from epithelial cystic linings or via malignant transformation of benign OTs^[35^]. The ratio of benign to malignant OTs in this study (Table 2) is higher than in many previous studies globally^[7,9,13,14,24,25,27,28,34,36,37^] Although other higher ratios of the MOTs have been reported in Japan (10%) and Ethiopia (19.6%)^[2,7^]. These variations may be attributed to various reasons, such as the study methodologies and the difficulty in making a correct diagnosis of these malignant tumors due to the lack of appropriate diagnostic criteria in the older WHO classifications of OT^[9^].

Only two types of MOTs were encountered in this study. The AC constituted the majority (12.5%), followed by CCOC (2%). This finding is similar to a report from a Brazilian study^[24^]. It also conformed to many other studies that reported AC as the commonest MOT^[9,13,24,28,35^]. On the other hand, some authors have reported IOSCC as the commonest MOT in their study^[2^].

Among the MOTs seen in this study, the frequency of occurrence of AC was highest in the young adult group (20–29 years), followed by the middle-aged group, while the majority of the clear cell odontogenic carcinomas were seen within the middle-aged adults (Table 3). This is in support of previous Nigerian studies^[12,18^].

The OT appears to have a higher preponderance in the mandible in this survey (Table 4). These findings are in line with those of other studies^[7,8,11,13,25,38^]. Among the BOTs, benign epithelial OTs (ameloblastoma and CEOT) were frequently seen to occur in the mandible (Table 4). On the contrary, over 90% of AOT occurred in the maxilla. This corresponds with findings from other parts of the world, including Nigeria^[12,13,23^]. Contrary to these findings, Kokubun et al^[7^] reported AOT to be more in the mandible, while Jing et al^[30^] reported equal distribution between the two jaws.

The benign mesenchymal OTs (odontogenic fibroma and odontogenic myxoma) and the benign mixed epithelial and mesenchymal tumors (ameloblastic fibroma and odontoma) were all found to be common in the mandible. This appears similar to previous studies^[7,12,13^]. Although Aregbesola et al^[13^] reported an equal prevalence of odontoma in the two jaws, Kokubun et al^[7^] and Nalabolu et al^[4^] both found odontoma to be common in the maxilla. The MOTs occurred more in the mandible than in the maxilla in this study (Table 4). This agrees with other Nigerian studies reporting a high distribution of AC in the mandible^[12,13,35^].

In a previous study on AC conducted at the researchers’ center^[39^], the ratio of distribution between the mandible and maxilla was 14.5:1, which is more than that found in this current study (9.6:1). This current ratio could be due to additional cases of AC involving the maxilla that presented after the initial research was completed, hence reducing the previous ratio.

One of the limitations of this study is that it is a single institution-based study, which affects the generalization of the findings to broader populations universally. Second, it did not provide further clinical information, such as follow-up conditions of the cases. Despite these, taking into account the importance of epidemiological studies in bringing up the definite characteristics and distribution of the disease in a specific environment and thus the development of tailored interventions, this study provides necessary information to the local Nigerian population regarding the OTs. This information will increase suspicion index among clinicians, thus aiding in early diagnosis and management of OTs in Nigeria.

Conclusion

This study provided insight into the occurrence of OTs in the Southeast Nigerian population using the 2022 WHO classification of OTs. Our findings revealed that BOTs were much more common in the study setting, with a slight female predilection and a high tendency to occur in the mandible. This paper also noted that ameloblastoma was the most common OTs, while AC was the most common malignant type.

Ethical approval

Ethical clearance was obtained from the Health Research Ethics Committee of the University of Nigeria Teaching Hospital, Enugu, Nigeria, and permission to conduct the study was obtained from the appropriate authorities of the department.

Consent

Written informed consent was obtained from the patient (and, in the case of minors, from the patient’s parents or legal guardian) for the publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Sources of funding

This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Author contributions

U.C.O.: Methodology, Validation, Investigation, Resources, Writing – original draft, Writing – review & editing, Project administration; O.D.I.: Methodology, Resources, Data curation, Writing – review & editing, Supervision; A.C.J.: Methodology, Resources, Data curation, Writing – review & editing, Supervision; I.O.: Methodology, Resources, Data curation, Writing – review & editing, Supervision; K.S.S.: Conceptualization, Methodology, Validation, Investigation, Resources, Data curation, Formal analysis, Writing – original draft, Writing – review & editing.

Conflicts of interest disclosure

The authors declare that they have no financial conflict of interest with regard to the content of this report.

Guarantor

Karpal Singh Sohal.

Research Registration Unique Identifying Number (UIN)

The study was registered with the University of Nigeria Registry UIN: NHREC/05/01/2008B-FWA00002458-1RB00002323.

Provenance and peer review

Not commissioned, externally peer-reviewed.

Data availability statement

The datasets generated during and/or analyzed during the current study are available upon reasonable request from the authors.