YIJOM-3869; No of Pages 7 Please cite this article in press as: Eljabo N, et al. Genetic and epigenetic alterations in the tumour, tumour margins, and normal buccal mucosa of patients with oral cancer, Int J Oral Maxillofac Surg (2018), https://doi.org/10.1016/j.ijom.2018.01.020 Research Paper Head and Neck Oncology Genetic and epigenetic alterations in the tumour, tumour margins, and normal buccal mucosa of patients with oral cancer N. Eljabo, N. Nikolic, J. Carkic, D. Jelovac, M. Lazarevic, N. Tanic, J. Milasin: Genetic and epigenetic alterations in the tumour, tumour margins, and normal buccal mucosa of patients with oral cancer. Int. J. Oral Maxillofac. Surg. 2018; xxx: xxx–xxx. ã 2018 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. N. Eljabo 1 , N. Nikolic 1 , J. Carkic 1 , D. Jelovac 2 , M. Lazarevic 2 , N. Tanic 3 , J. Milasin 1 1 Institute of Human Genetics, School of Dental Medicine, University of Belgrade, Belgrade, Serbia; 2 Clinic for Maxillofacial Surgery, School of Dental Medicine, University of Belgrade, Belgrade, Serbia; 3 Laboratory for Radiobiology and Molecular Genetics, Institute of Nuclear Sciences ‘‘Vinca’’, University of Belgrade, Belgrade, Serbia Abstract. Despite adequate surgical resection, oral squamous cell carcinoma (OSCC) shows a high rate of recurrence and metastasis, which could be explained by the presence of molecular alterations in seemingly normal tumour margins and the entire oral mucosa. The aims of this study were (1) to assess the presence of gene amplification (c-Myc and HER2) and promoter methylation (p14 and p16) in the tumours, tumour margins, and unaffected oral mucosa of 40 OSCC patients, and (2) to evaluate the possibility of using these alterations as prognostic markers. c-Myc and HER2 genes were quantified by means of real-time PCR (qPCR), and p14 and p16 methylation status was determined by methylation-specific PCR (MSP PCR). All tissues examined exhibited molecular alterations in various proportions. Tumour tissues, as expected, showed the highest prevalence of alterations, while oral mucosa showed the lowest. Multiple alterations (co-alterations) in tumours and tumour margins were significantly more frequent than in unaffected oral mucosa (P < 0.001 and P = 0.027, respectively). HER2 amplification in margin tissue (P < 0.001) and swabs (P = 0.013), as well as the existence of three co-alterations in margins (P = 0.001) and macroscopically unaffected oral mucosa (P < 0.001) were correlated with shorter disease-specific survival. Key words: gene amplification; promoter hy- permethylation; OSCC; tumour margin; field cancerization. Accepted for publication 26 January 2018 Squamous cell carcinoma (SCC) is one of the most common malignancies in the oral cavity 1 . The early stages of the disease, which have a good prognosis, are usually asymptomatic. Thus most cases are diag- nosed at an advanced stage 2 , characterized by a poor prognosis and low survival. De- spite advances in diagnosis and therapy, the incidence of recurrence, local and distant metastasis, andmortalityratesremainhigh 1 . Oral squamous cell carcinoma (OSCC) arises as a result of the accumulation of Int. J. Oral Maxillofac. Surg. 2018; xxx: xxx–xxx https://doi.org/10.1016/j.ijom.2018.01.020, available online at https://www.sciencedirect.com 0901-5027/000001+07 ã 2018 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.