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Odontogenic tumours in children and adolescents: a review of forty-eight cases.

Objectives: Odontogenic tumours comprise a large heterogeneous group of lesions originating from odontogenic epithelium and/or ectomesenchyme and its vestiges. The aim of this study was to analyze odontogenic tumours in children and adolescents seen at a tertiary institution in South Western Nigeria and compare with results from previous studies. Material and Methods: Archival records of the Department of Oral Pathology, University College Hospital Ibadan were reviewed. All histologically diagnosed odontogenic tumours in patients 19 years and below spanning a period of 21 years (1990-2011) were retrieved. Data regarding age, gender, and tumor topography were analyzed using SPSS for Window (version 18.0; SPSS Inc. Chicago, IL) Results: One hundred and forty seven jaw swellings were seen in children and adolescents aged 19 or less during the study period, out of which 48 (32.7%) were odontogenic tumours. More cases were seen in males than females with a male: female ratio of 7:5. The mandible was the commonest site of occurrence with mandible: maxilla ratio of 11:4. Ameloblastoma was the commonest odontogenic tumours with 14 (29.1%) solid ameloblastoma and 9 (18.8%) cystic ameloblastoma cases followed by fibromyxoma with 8 (16.7%) cases. calcifying epithelial odontogenic tumour , calcifying cystic odontogenic tumour and odontogenic fibroma were occasionally seen. Conclusion: This study showed that ameloblastoma was the most common odontogenic tumour in children and no case of odontoma was seen. Odontogenic tumours in children and adolescents may not be as rare as previously reported by some authors and inclusion of keratocystic odontogenic tumour in this study slightly affected the relative incidence of odontogenic tumors in children and adolescents.


INTRODUCTION
Odontogenic tumours comprise a large heterogeneous group of lesions originating from odontogenic epithelium and or ectomesenchyme and its vestiges. 1 Odontogenic tumours include entities of hamartomatous nature (for example, odontoma), benign neoplasms, some of which are aggressive (for example, ameloblastoma and myxoma) and malignant neoplasms capable of metastasis. 2,3 Odontogenic tumours accounted for between 1% and 28% of oral lesions from various studies depending on the criteria and categories that were used for comparison. 4 Odontogenic keratocysts were recently included in the WHO classification of odontogenic tumours as keratocystic odontogenic tumours based on its clinical behaviour, genetic and molecular features. 5 Previous reports examined odontogenic tumours in children as part of oral tumors 6,7,8 or studied individual tumors such as ameloblastomas 9 and adenomatoid odontogenic tumour (AOT) 10   Fibromyxoma Fibromyxoma was the second most common lesion with a mean age of occurrence of 14.8 (±5.5) years (range 3-19 years). There was a male preponderance with male to female ratio of 6:2 but an equal site distribution of 4:4.

Ameloblastic fibroma
The mean age of occurrence for AF was 16.0 (±2.5) years (range 14-19 years). The lesion was seen only in males and occurred exclusively in the mandible.

AOT
The age range for AOT was 12-18 years with mean age of 15.0 (±2.5) years. The lesion had no sex preponderance in this series (male to female ratio 2:2). All four cases were seen in the maxilla.

KOT
The four cases of KOT seen had a mean age of 12.75 (±2.50) years (range 10-16 years). KOT was seen more in females with a male to female ratio of 1:3 and had a mandibular predilection (mandible: maxilla ratio 3:1).

CEOT/CCOC
Two cases of CEOT were seen with a mean age of 16.5 (±0.7) (range [16][17]. The lesion had no sex or site predilection. (Table 1) CCOC occurred exclusively in females and was only seen in the mandible. The mean age was 15 (±2.83) years (range 13-17 years).

OF
The only case of odontogenic fibroma was seen in a 13-year-old female and it was also the only case of exraosseous tumour in this study.

DISCUSSION
Previous reports found odontogenic tumours to be rare in children and adolescents. 12 Comparing results regarding the relative prevalence of odontogenic tumours in children with previous studies may be difficult because different studies used dissimilar ages to categorize odontogenic tumours in children and these groups were varied over a wide spectrum of oro-facial lesions. 12 Most studies were in agreement with our finding of male predilection 6,11,12 except for ulmansky 14 who reported a female preponderance.
Ameloblastoma was the most common odontogenic tumour in children and adolescents with a total of 48% of cases. Previous studies report ameloblastoma to be the most common odontogenic tumour both in general population and in children; Ajayi et al 11 in Lagos reported that ameloblastoma constituted 48.9% of odontogenic tumours in children while Adebayo et al 12 in Kaduna reported a slightly higher figure of 54% of odontogenic tumours in their series. Other authors found odontomas to be the commonest odontogenic tumours in children and adolescents with Guerrisi 4 in Argentina reporting 50.9% of odontogenic tumours as odontomas while ameloblastoma accounted for just 18.3% of odontogenic tumours in their series. Although unicystic ameloblastoma is said to be more commonly seen in the second and third decades of life 17 , the solid ameloblastoma (29.2%) was more common than the unicystic type (18.8%) but this was higher than the 11% reported by Ajayi et al. 11 Fibromyxoma with 16.7% of cases was the second most common odontogenic tumour in this series. Adebayo et al 6 also found fibromyxoma to be the second commonest odontogenic tumour in children with 19% of cases in their series but Ajayi et al 11  The male predominance in this series is at variance with most previous studies which showed a female predilection 11,12,14 but the equal mandible/maxilla distribution in this study, was corroborated by other studies. 11,12,14 Ameloblastic fibroma accounted for 8.3% of odontogenic tumours in this series. Other studies have reported between 1% and 8% of odontogenic tumours to be AF 11,12 . The male and mandibular predilection is in agreement with most other reports except for Ajayi et al 11 who found a female predominance.
We found 4 (8.3%) cases of KOT in this study; previous publications did not include KOT in their reports 11,12,15,16 either because they used older WHO classifications of oral tumors that considered KOT as a cystic lesion, or as Guerrisi et al 4 claimed, for easy comparison with other studies. The finding that KOT affected more female than males is at variance with previous studies. 18 AOT was the second and third most common odontogenic tumors in children in previous Nigerian studies from Lagos 11 and Kaduna 6 constituting 19.6% and 9% in their respective studies. This was slightly different in this study with AOT accounting for 8.6% of cases. AOT was exclusively seen in the maxilla in this series; which was in keeping with several other studies. 6,10,11,14 Only one case of OF was diagnosed in children in this series. Adebayo et al 6 did not report any case of OF in their study while Arotiba in Ibadan 16 reported only two in their series. In contrast, Arotiba in Lagos 7 and Guerrisi in Argentina 4 reported four and five cases respectively.
Odontomas and malignant odontogenic tumours were not seen in this study which was in conformity with previous studies from Nigeria which either found few or no cases 6,11,16 but at variance with some other studies that showed odontomas to be the commonest odontogenic tumours in their series 14 . Odontomas may be under reported, as it is usually asymptomatic and frequently diagnosed by routine panoramic radiographic examination that is not yet a routine in most clinical settings in Nigeria.
This study reviewed odontogenic tumours in children and adolescents using the WHO 2005 classification with results conforming relatively to the demography of the different tumor types in previous publications. The inclusion of KOT in this series appears to have affected the relative occurrence odontogenic tumours compared to previous studies but the demography of odontogenic tumours were essentially similar to those of previous studies. We conclude that odontogenic tumours in children and adolescents may not be as rare as previously reported by some authors, though, the higher age limit considered and the inclusion of KOT in this series may have accounted for the relatively higher percentage of odontogenic tumours in children in this study.