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What Is Colon Cancer?What is Colon Cancer? Colon cancer or colorectal cancer is a malignant tumor that arises typically from the inner lining of the lower part of the digestive tract, the large intestine (colon) and rectum. These tumors are quite common in the US and most of the world and therefore account for a significant amount of death and disability.
What is the colon?The digestive tract (or gastrointestinal tract) is a essentially a long tube starting at our mouth and ending at the anus. It is important for ingestion, digestion and then absorption of nutrients from the food we eat. While the early parts of the tube are important for taking the food in and digesting it into small bits, the later parts are important for absorption of the nutrients found in that food. The colon, also known as the large intestine, is the last part of that digestive tube before the anus. It is a large, thick tube through which digested food passes. In this area water and some electrolytes are absorbed. What is left is solid feces. The colon ends in the rectum where this solid feces is stored until it is passed in a bowel movement (defecation). The lining cells of the intestine, called the mucosa are the most common origin for these tumors. When these cells develop enough mutations to become a cancer, they start dividing uncontrollably, forming a mass. These tumors can develop anywhere within the large intestine and rectum. Commonly, early tumors form what is called a colonic polyp, a small, mushroom-like growth on the inner wall of the colon. As these polyps aquire more mutations, some can eventually develop into a cancer. Therefore, polyps, although not cancer themselves, are a risk factor for cancer and are an important part of the development of what is colon cancer. Colon cancers can arise anythere within the colon. The colon starts at the end of the small intestine and ends at the rectum just before the anus. These tumors can develop along any of the mucosa that lines this entire area. They do not arise from the anus itself or from the small intestine. However, other types of cancers can involve these structures.
The most common type of cancer in the colon is an adenocarcinoma. This is the name for a cancer arising from gland tissue or tissues that secrete things. Because the lining of the colon has glands and cells that secrete mucous and other things important for the digestive system, these tumors are called adenocarcinomas. However, adenocarcinomas are not exclusive to the colon. For example, lung adenocarcinoma, stomach adenocarcinoma and others are common forms of cancer.
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