Impact of changing classification systems on prevalence and frequency distribution of odontogenic tumors in tertiary care center of Nagpur

INTRODUCTION: The classification of odontogenic tumors has been revised from time to time in order to provide unified terminology. This reclassification had considerable impact on their prevalence and frequency distribution. OBJECTIVES: This study was aimed to emphasize impact of changing classification systems on prevalence and relative frequency of odontogenic tumors. The secondary objective was to analyze demographics of various histological types of odontogenic tumors in comparison to published literature. Review of Indian studies (1992–2020) elaborating frequency of odontogenic tumors is summarized in the end. METHODS: This was a hospital-based retrospective study wherein case files of odontogenic tumors diagnosed from 1990 to 2019 period were retrieved. The classification system used originally at the time of diagnosis was retained and prevalence of odontogenic tumors in three different periods (1990–2004, 2005–2016 and 2017–2019) was compared. Further, prevalence, frequency distribution and demographics of all these tumors (1990–2019) were analyzed using latest World Health Organization 2017 classification. RESULTS: A total of 345 odontogenic tumors was diagnosed as per World Health Organization 2017 system of classification from 1990 to 2019. 96.81% tumors were benign and 3.81% constituted malignant odontogenic tumors. However, there was marked increase in prevalence of odontogenic tumors in 2005–2016 (6.2%) period as compared to 1990–2004 (3.87%) and 2017–2019 (3.47%). Ameloblastoma remained the most common tumor in three different periods, whereas keratocystic odontogenic tumor became second commonest tumor in 2005–2016 as compared to odontoma in 1990–2004 and adenomatoid odontogenic tumor in 2017–2019. CONCLUSIONS: The continuous evolving systems of classification may partly be responsible for inconsistency in odontogenic tumors, with inclusion of keratocystic odontogenic tumor,and has marked impact on prevalence and frequency distribution of odontogenic tumors. The geographical variations in demographics of odontogenic tumors might reflect genetic and environment influence; however it requires elucidation by further studies.