West Asia Organization for Cancer Prevention (WAOCP), APOCP's West Asia Chapter. Asian Pacific Journal of Cancer Prevention 1513-7368 24 8 2023 08 01 Primordial Odontogenic Tumor; Archival Review of 19380 Cases in a 55-Year Retrospective Study 2845 2853 90766 10.31557/APJCP.2023.24.8.2845 EN Mohammadfazel Ranjbar Dental Student, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran. Monir Moradzadeh Khiavi Oral and Maxillofacial Pathology Department, Tehran University of Medical Sciences, Tehran, Iran. 0000-0003-4170-9596 Mojgan Ghazi Oral and Maxillofacial Pathologist, Tehran, Iran. Samira Derakhshan Oral and Maxillofacial Pathology Department, Tehran University of Medical Sciences, Tehran, Iran. Cancer Preclinical Imaging Group, Preclinical Core Facility, Tehran University of Medical Sciences, Tehran, Iran. 0000-0003-4373-9043 Journal Article 2023 04 21 Background and Objective: Primordial odontogenic tumor is a rare odontogenic tumor reported for the first time in 2014. It was included in the latest edition of World Health Organization classification of Head and Neck Tumors as a new benign mixed epithelial-mesenchymal neoplasm. To date, 26 cases has been reported in literature. The aim of this study was to determine the possible presence of primordial odontogenic tumor in the previously diagnosed cases with myxoid stroma. Materials and Methods: This study was a retrospective descriptive study that was concluded in Oral and Maxillofacial Pathology Department, School of Dentistry, Tehran University of Medical Sciences. We reviewed all 19,380 cases from 19,66 to find the lesions with myxoid stroma which were in differential diagnosis with primordial odontogenic tumor. These cases should be associated with an impacted or unerupted tooth and belong to the patients under 20 years old. Results: We find 503 pericoronal lesions with myxoid stroma. Three cases were isolated after recut and reevaluation for finding fulfill histologic features. After immunohistochemical analysis, we find a new case of developing primordial odontogenic tumor associated with odontoma. Discussion: Primordial odontogenic tumor a recently described odontogenic tumor has a well-defined clinicopathological and immunohistochemical profile and should be differentiated from the others pericoronal lesions. It is the first time that this archival review has been done to find probable cases of primordial odontogenic tumor. https://journal.waocp.org/article_90766_573b0ecb09cef31bc48ff16ca299134b.pdf