The sample to be studied will consist of approximately 90-100 individuals in normal risk for developing CRC aged 50-75 years, will undergo preventive colonoscopy for polyps and CRC detection. Participants will be divided into three groups of patients according to the findings during endoscopy: those without pathological findings, those with polyps between 1 to 3 centimeters diameter and adenomatous elements in pathology examination and finally those with colorectal cancer. From all these three populations, samples would be collected from peripheral blood (plasma) and colon tissue biopsy (normal or abnormal, respectively) in order to find a possible common mutations of some genes involved in the pathogenesis of the CRC in these 3 groups [e.g. in KRAS12, 13, 61, BRAF (V600E), ccfDNA some point mutations in hMLH1]. The samples of blood and tissue will be placed in a blood bottle with a specific anticoagulant and preservative (RNA latter) and subsequently stored at -20 degrees for maintenance. The genome analysis of potential mutations will be done by specific commercial DNA kit and specific PCR techniques. Then according to the results, it will be carried out a try to present statistically significant elements compatible or not with the original purpose of the investigation.