Objective: Neuroendocrine tumors develop from the neuroendocrine cells of the endocrine system. As these tumors are extremely slow growing compared with other cancers, they often take years to reach a measurable dimension, thus leading to the late diagnosis, which has adverse effects on the survival and quality of life of patients. There is a link between many types of cancer and genomic instability, thus the markers associated with genomic instability can be used for early diagnosis of the disease or cancer-related changes. Comet assay is the most commonly used method to test genomic instability or DNA damage. To the best of our knowledge, no data are available on DNA damage in patients with neuroendocrine tumors. This study aimed to investigate the possible risk of DNA damage in a patient with neuroendocrine tumors using the comet assay.