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The 5th edition of the World Health Organization (WHO) Classification of Head and Neck Tumors opened to online access in March 2022. This edition is conceptually similar to the previous classification of odontogenic lesions. The only newly defined entity in odontogenic lesions is adenoid ameloblastoma, which is classified under benign epithelial odontogenic tumors. While not odontogenic, the surgical ciliated cyst is a new entry to the cyst classification of the jaws. In other respects, a very important change was made in the new blue books that added 'essential and desirable diagnostic criteria' for each entity to highlight the features considered indispensable for diagnosis. In this article, we review the odontogenic tumors and cysts of the jaw sections of the Odontogenic and Maxillofacial Bone Tumors Chapter, outlining changes from the 2017 WHO classification and summarizing the essential diagnostic criteria and new developments. [ABSTRACT FROM AUTHOR]

The 4th edition of the World Health Organization (WHO) Classification of Head and Neck Tumors was published in January 2017. The edition serves to provide an updated classification scheme and extended genetic and molecular data that are useful as diagnostic tools for the lesions of the head and neck region. This review focuses on the most current update of odontogenic cysts and tumors based on the 2017 WHO edition. The updated classification has some important differences from the 3rd edition (2005), including a new classification of odontogenic cysts, 'reclassified' odontogenic tumors and some new entities. [ABSTRACT FROM AUTHOR]

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Cairns L, Naidu A, Robinson C M, Sloan P, Wright J M & Hunter K D (2010) Histopathology 57, 544-548 CD56 (NCAM) expression in ameloblastomas and other odontogenic lesions Aims: Ameloblastomas recapitulate certain elements of tooth formation. CD56 is expressed by a variety of cells and is used in tumour diagnosis, but is also expressed in the enamel organ during tooth development. The aim of this study was to describe the expression of CD56 in odontogenic lesions with particular reference to the differential diagnosis of ameloblastoma and odontogenic keratocyst. Methods: Cases were selected from the pathology archives at Glasgow Royal Infirmary, Glasgow, Royal Victoria Infirmary, Newcastle and Department of Diagnostic Sciences, Texas A&M Health Science Center Baylor College of Dentistry, Dallas. The study population included 38 ameloblastomas, 19 odontogenic keratocysts and a number of other odontogenic lesions, including nine compound odontomes. All sections were examined for CD56 immunoreactivity and the extent of staining was recorded. Results: Thirty-seven of 38 (97%) ameloblastomas expressed CD56 on the cell membrane of peripheral cells in tumour nests (16 extensively, 21 focally). Immunoreactivity was lost in areas of inflammation, acanthomatous differentiation, in areas of cystic change and upon fusion with overlying surface epithelium. One odontogenic keratocyst expressed CD56 (5%, P < 0.0001). CD56 was expressed very focally in two odontomes, exclusively in stratum intermedium-like cells. Conclusions: CD56 expression in odontogenic epithelium is highly suggestive of ameloblastoma and can help in differentiating this from odontogenic keratocyst. [ABSTRACT FROM AUTHOR]