What is the disease?
Colon and rectal cancer develop in the digestive tract, which is also called the gastrointestinal, or GI, tract. The digestive system processes food for energy and rids the body of solid waste matter (fecal matter or stool). Colon cancer and rectal cancer have many features in common. Sometimes they are referred to together as colorectal cancer. Over 95% of colorectal cancers are ad enocarcinomas. These are cancers of the glandular cells that line the inside of the colon and rectum. Other, less common type of tumors may also develop in the colon and rectum. Carcinoid tumors develop from hormone-producing cells of the intestine. Gastrointestinal stromal tumors develop in the connective tissue and muscle layers in the wall of the colon and rectum. Lymphomas are cancers of immune system cells that typically develop in lymph nodes but may also start in the colon and rectum or other organs. Colorectal cancers are thought to develop slowly over a period of several years. Before a true cancer develops, there usually are precancerous changes in the lining of the colon or rectum. These changes might be dysplasia or adenomatous polyps. A polyp is a growth of tissue into the center of the colon or rectum. Some types of polyps (hyperplastic polyps and inflammatory polyps) are not precancerous. However, having adenomatous polyps, also known as adenomas, does increase a person's risk of developing cancer, especially if there are many polyps or they are large. In contrast to the inward growth of a polyp, a true cancer can grow inward toward the hollow part of the colon or rectum, and/or outward through the wall of these organs. If not treated, cells from the tumor may break away and spread through the bloodstream or lymph system to other parts of the body. There, they can form "colony" tumors. This process is called metastasis. The colon has four sections. The first section is called the ascending colon. 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. Each of these sections of the colon and rectum has several layers of tissue. Colorectal cancers start in the innermost layer and can grow through some or all of the other layers. Knowing a little about these layers is important, because the stage (extent of spread) of a colorectal cancer depends to a great degree on which of these layers it affects. What organs does the disease affect and what are their actions? ·
Stage 0. The cancer is very early. It is found only in the innermost lining of the colon or rectum. ·
Stage I. The cancer involves more of the inner wall of the colon or rectum. ·
Stage II. The cancer has spread outside the colon or rectum to nearby tissue, but not to the lymph nodes. ·
Stage III. The cancer has spread to nearby lymph nodes, but not to other parts of the body. ·
Stage IV. The cancer has spread to other parts of the body. Colorectal cancer tends to spread to the liver and/or lungs. ·
Recurrent. Recurrent cancer means the cancer has come back after treatment. The disease may recur in the colon or rectum or in another part of the body. The organs and their purpose are best described in the following example of the digestive system and the functions of the intestines, colon and rectum. After food is chewed and swallowed, it travels through the esophagus to the stomach. There it is partly broken down and then sent to the small intestine, also known as the small bowel. The word "small" refers to diameter of the small intestine, which is narrower than that of the large bowel....
Cited: National Cancer Institute, http://cancernet.nci.nih.gov/wyntk_pubs/colon.htm
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