Tehran University of Medical Sciences International Journal of Hematology-Oncology and Stem Cell Research 2008-2207 11 3 2017 07 02 251 262 EN Leila Hamzehzadeh Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Meysam Yousefi Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. AND Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran Seyed Ghaffari Hematology, Oncology and Stem Cell Transplantation Research Center, Shariati Hospital, Tehran University of Medical Sciences, Tehran, Iran 2016 05 06 2016 09 29 Colorectal cancer (CRC) is one of the most common cancers worldwide and considered to be one of the hassle in medical communities. CRC develops from precancerous polyps in the colon or rectum and is preventable and curable by an early diagnosis and with the removal of premalignant polyps. In recent years, scientists have looked for inexpensive and safe ways to detect CRC in its earliest stages. Strong evidence shows that screening for CRC is a crucial way to reduce the incidence and mortality of this devastating disease. The main purpose for screening is to detect cancer or pre-cancer signs in all asymptomatic patients. In this review, we holistically introduce major pathways involved in the initiation and progression of colorectal tumorgenesis, which mainly includes chromosome instability (CIN), microsatellite instability (MSI), the CpG island methylator phenotype (CIMP), and we then will discuss different screening tests and especially the latest non-invasive fecal screening test kits for the detection of CRC. https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/view/610 https://ijhoscr.tums.ac.ir/index.php/ijhoscr/article/download/610/566