Original Article 158 Received : 15.04.2017 Accepted : 23.11.2017 Correspondence: Azade ANDISHE TADBIR Shiraz University of Medical Sciences, School of Dentistry, Department of Oral and Dental Disease, SHIRAZ, IRAN E-mail: jeiroodi@yahoo.com Phone: +98 917 703 13 78 doi: 10.5146/tjpath.2017.01421 (Turk Patoloji Derg 2018, 34:158-164) ABSTRACT Objective: Midkine is a heparin-binding growth factor whose expression is increased in most tumors, namely ameloblastomas. This study aimed to compare Midkine expression in different odontogenic lesions. Material and Method: This analytical cross-sectional study was performed on 52 definitely diagnosed odontogenic lesions including 15 dentigerous cysts, 13 odontogenic keratocysts, and 17 unicystic and 5 multicystic ameloblastomas archived from 1997 to 2015. Midkine expression was examined in tissue samples through immunohistochemistry. The nonparametric Kruskal-Wallis and Mann-Whitney tests were run as appropriate (P < 0.05). Results: The frequency of Midkine expression was < 20% in 7.7%, 20-50% in 25%, and > 50 % in 67.3% of the samples, indicating significant differences among the groups (P = 0.002). Moreover, the expression intensity was strong in 63.5%, moderate in 23.1%, and weak in 13.5% of odontogenic lesion samples (P = 0.071). The total staining score was weak in 3.8%, moderate in 48.1%, and strong in 48.1% of the cells, displaying significant differences between the study groups in this regard (P = 0.043). Conclusion: Midkine can be considered as both a differentiating factor and a molecular-targeted therapy in odontogenic lesions. Yet, further studies are required to approve the role of this cytokine in different biological and pathological stages of the tumors. Key Words: Dentigerous Cysts, Odontogenic Keratocyst, Ameloblastoma, Unicystic, Multicystic Evaluation of Midkine Expression in Dentigerous Cysts, Odontogenic Keratocysts and Different Types of Ameloblastoma Naghmeh JEIROODI 1 , Mahshid BAGHERPOUR 1 , Razieh ZARE 1 , Shima TORABI ARDAKANI 1 , Azadeh ANDISHEH TADBIR 2 Department of 1 Oral and Maxillofacial Pathology and 2 Oral and Dental Disease, School of Dentistry, Shiraz University of Medical Sciences, SHIRAZ, IRAN INTRODUCTION Odontogenic cysts are important pathologic lesions of the oral cavity. Among the most prevalent developmental odontogenic jaw cysts are dentigerous cysts (follicular). These occur as a result of fluid accumulation between the tooth crown and reduced enamel epithelium. It is treated through enucleation and extraction of the involved tooth. The prognosis of a dentigerous cyst is excellent and rarely does it recur. An odontogenic keratocyst is a relatively common developmental odontogenic jaw cyst originating from the remnants of dental lamina. Due to the genetic features, tendency to recur, and high aggressiveness according to WHO classification, the parakeratinized variant of odontogenic keratocysts is classified as a benign odontogenic tumor (1-3). Ameloblastoma is a generally benign odontogenic tumor of the jaw bone. Yet, it is quite likely to relapse after extensive surgeries. Ameloblastoma is more prevalent in the mandible than the maxilla; and rarely does it occur in an extraosseous location. Malignant ameloblastoma is quite uncommon. The etiology is still unknown. Its occurrence rate is estimated to be 0.5 in one million in a year; however, this number is estimated to be much higher in some regions such as South Africa (4-6). Most patients are 30-60 years old when diagnosed. There is no difference between the sexes concerning the distribution of the disease. Bony septa may result in a honeycomb appearance (7). Clinically and radiographically, ameloblastomas are divided into the three clinical groups of unicystic, peripheral, and solid/ multicystic, the last of which is the most frequent (8). The multifunctional cytokine, Midkine, is a heparin- binding growth factor with low molecular weight (13 kilodalton). It contributes to formation of different organs through mesenchymal-epithelial interactions (9-12). Although the role and biological effective mechanisms of Midkine are not crystal clear, its angiogenic role in tumorigenesis has been well proven (12).