Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine).[5] Signs and symptoms may include blood in the stool, a change in bowel movements, weight loss, abdominal pain and fatigue.[9] Most colorectal cancers are due to old age and lifestyle factors, with only a small number of cases due to underlying genetic disorders.[2][3] Risk factors include diet, obesity, smoking, and lack of physical activity.[2] Dietary factors that increase the risk include red meat, processed meat, and alcohol.[2][4] Another risk factor is inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis.[2] Some of the inherited genetic disorders that can cause colorectal cancer include familial adenomatous polyposis and hereditary non-polyposis colon cancer; however, these represent less than 5% of cases.[2][3] It typically starts as a benign tumor, often in the form of a polyp, which over time becomes cancerous.[2]

Reference
Wiki: Colorectal neoplasm