It extends upward on the right side of the abdomen. The second section is called the transverse colon since it goes across the body to the left side. There it joins the third section, the descending colon, which continues downward on the left side. The fourth section is known as the sigmoid colon because of its S-shape. The sigmoid colon joins the rectum, which in turn joins the anus, or the opening where waste matter passes out of the body.
Colorectal cancer is malignant cells found in the colon or rectum.
The colon and the rectum are part of the large intestine, which is part of the digestive system. Because colon cancer and rectal cancers have many features in common, they are sometimes referred to together as colorectal cancer. Cancerous tumors found in the colon or rectum also may spread to other parts of the body. Colorectal cancer is the second leading cause of cancer deaths in the United States. However, the number of new cases of colorectal cancer, and the number of deaths due to colorectal cancer, have decreased, which is attributed to increased sigmoidoscopic screening and polyp removal.