Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 12 2 2020 12 16 98 108 Haniyeh Rafipour Cancer Biology Research Center, Tehran University of medical sciences, Tehran, Iran. Elham Mohebbi Pathology and Stem Cell Research Center, Kerman University of Medical Sciences, Kerman, Iran. Kazem Zendehdel Cancer Biology Research Center, Tehran University of medical sciences, Tehran, Iran. Samad Muhammadnejad -Cell-Based Therapies Research Center, Digestive Diseases Research Institute, Tehran University of Medical Sciences, Tehran, Iran. Paria Akbari School of medicine, Tehran University of Medical Science, Tehran, Iran. Saadeh Hashemi Cancer Biology Research Center, Tehran University of medical sciences, Tehran, Iran. Kosar Nouri Department of Regenerative Medicine, Cell Science Research Center, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran Fatemeh Moradkhani Department of Medicinal Chemistry, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran Tahereh Barati Research Center for Advanced Technologies in Cardiovascular Medicine, Tehran University of Medical Sciences. Saeid Amanpour Cancer Biology Research Center, Tehran University of medical sciences, Tehran, Iran. 2020 08 09 2020 12 04 Several epidemiological studies have reported that regular use of opium can be associated with an increased risk of developing cancers, including oesophageal, laryngeal, bladder, lung, and gastric cancer. In this systematic review, we aimed at investigating whether experimental studies support this finding and, if yes, how opium consumption can cause cancer. Most of the articles that have studied opium or its derivatives have found it as a carcinogen. However, due to the complex composition, different forms, and various ways of opium use, further comprehensive experimental studies are required. Using modern genomic and epigenomic methods seems to help determine the molecular mechanisms underlying opium carcinogenicity. https://bccr.tums.ac.ir/index.php/bccrj/article/view/359