Most cases of colon cancer begin as a set of small, non-cancerous (benign) cells called an «Adenomatous polyp». Over time, some of these polyps may develop into colon cancer.
Colorectal cancer originates in the innermost layer (the mucosa) and can grow outward through some or all of the other layers. When the cancer cells are in the wall, they can grow into the blood vessels or lymph vessels. From there, cancer cells can move to nearby lymph nodes or distant parts of the body.
Many people with colon cancer do not have any symptoms in the early stages of the disease.