Critical assessment of the latest classification of jaw cysts proposed by the World Health Organization (2017)

Background: The fourth edition of the World Health Organization Classification of Head and Neck Tumors was published in January 2017, and includes a classification of odontogenic tumors and odontogenic cysts. The present review assesses the changes made in this new classification in relation to odontogenic and non-odontogenic jaw cysts.

Material and methods: An electronic search was conducted in the Cochrane Library, PubMed-MEDLINE and Scopus databases using the search terms: "odontogenic cyst" "WHO classification" "update". Studies written in English and published between January 2005 and April 2020 with a high level of scientific evidence were included, while studies not published in English, epidemiological studies, and studies with a low level of scientific evidence were excluded.

Results: The initial search identified 311 articles, and after the deletion of duplicates, 7 studies were selected for full-text assessment. After excluding two studies that failed to provide relevant information and had a low level of scientific evidence, 5 articles were finally included and stratified according to their level of scientific evidence based on the SORT (Strength of Recommendation Taxonomy) criteria.

Conclusions: The incorporation of odontogenic and non-odontogenic cysts to the head and neck tumors classification underscores the recognition of the WHO of these important disorders of the jaws. Based on the current evidence, there is controversy as to whether odontogenic keratocysts should be regarded as cystic lesions or as neoplasms, though there is no such controversy in relation to calcifying odontogenic cysts. On the other hand, orthokeratinized odontogenic cysts have been included in the classification as a single entity differentiated from odontogenic keratocysts, while residual cysts have been removed from the classification. Key words:Odontogenic cyst, WHO classification, pseudocyst.