Specific colon cancer causes are not clear at this point, but researchers have found several factors that can increase a person’s risk of colorectal cancer. In general, colon cancer begins when healthy cells in the colon develop changes or mutations in their DNA. A cell’s DNA contains a set of instructions that tell a cell what to do. Healthy cells grow and divide in an orderly way to keep your body functioning normally. But when a cell’s DNA is damaged and becomes cancerous, cells continue to divide even when new cells aren’t needed. As the cells accumulate, they form a tumor. With time, the cancer cells can grow to invade and destroy normal tissues nearby and cancer cells can travel to other parts of the body to form deposits there, which are metastasis.