Historical review of odontogenic tumors and histological differentiation of unicystic ameloblastoma and cystic lesions

Abstract

Odontogenic tumors originate from tooth­forming tissue cells and are specialized tu­ mors in oral regions. Due to the origin of the tissue cells of these tumors, they are divided into three groups : epithelial, non­epithelial and mixed tumors. In 1746 Pierre Fauchard first pub­ lished a description of the odontogenic tumor. This was followed by descriptions by Broca, and then Bland­Sutton who classified odontogenic tumors based on the structure of the tooth germ. In the 1930's the term ameloblastoma came into use, and then early in the 1950's the term odontoma came into general use. In 1971 WHO published the classification of odontogenic tu­ mors in book form. After that, they published revised editions in 1992, 2005 and 2017. Prior to the 2nd edition in 1992, the classification of odontogenic tumors was published in book form. In the 3rd edition in 2005 and the 4th edition in 2017, the classification was published as one chapter of head and neck tumors. In the 3rd edition in 2005, two lesions, the odontogenic kera­ tocyst (OKC) and the calcifying odontogenic cyst (COC), were classified as odontogenic tumors,which were referred to as the keratocystic odontogenic tumor (KCOT) and the calcifying cystic odontogenic tumor (CCOT) in alternative terminology. However, in the 4th edition in 2017, the terms KCOT and CCOT were restored to OKC and COC because of new information, including developmental molecular data. In addition, the names of three other lesions were deleted from the classification of odontogenic tumors in this edition. They were the odontoameloblastoma, the ameloblastic fibrodentinoma, and the ameloblastic fibro­odontoma, which were considered types of odontoma. Our hospital has had biopsy services from 1994 to the present. For 23 years from January 1994 to December 2016, we saw more than 20,000 cases. The most common was the cystic le­ sion, followed by carcinoma, and then inflammatory and odontogenic tumors, which were less common. Cystic lesions and unicystic ameloblastomas are not always easy to histopathologi­ cally diagnose in small biopsy specimens. However, it is not difficult to make the histopathologic diagnosis with whole sections. The larger the specimen, the easier the diagnosis, even in uni­ cystic ameloblastomas. Shika Igaku (J Osaka Odontol Soc) 2018 ;Mar ;81(1) : 1­10.