Alternate Names : Colorectal cancer, Cancer – colon, Rectal cancer, Cancer-rectum, Adenocarcinoma- colon, Colon -adenocarcinoma
Definition
Colon, or colorectal, cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon).
Other types of cancer can affect the colon, such as lymphoma, carcinoid tumors, melanoma, and sarcomas. These are rare. In this article, use of the term “colon cancer” refers to colon carcinoma only.
Overview, Causes, & Risk Factors
According to the American Cancer Society, colorectal cancer is one of the leading causes of cancer-related deaths in the United States. However, early diagnosis often leads to a complete cure.
Almost all colon cancer starts in glands in the lining of the colon and rectum. When most people and when doctors talk about colorectal cancer, this is generally what they are referring to.
There is no single cause for colon cancer. Nearly all colon cancers begin as noncancerous (benign) polyps, which slowly develop into cancer.
You have a higher risk for colon cancer if you:
- Are older than 60
- Are African American and eastern European descent
- Eat a diet high in red or processed meat
- Have cancer elsewhere in the body
- Have colorectal polyps
- Have inflammatory bowel disease (Crohn’s disease or ulcerative colitis)
- Have a family history of colon cancer
- Have a personal history of breast cancer
Certain genetic syndromes also increase the risk of developing colon cancer. Two of the most common are hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, and familial adenomatous polyposis (FAP).
What you eat may play a role in your risk of colon cancer. Colon cancer may be associated with a high-fat, low-fiber diet and red meat. However, some studies found that the risk does not drop if you switch to a high-fiber diet, so the cause of the link is not yet clear.
Smoking cigarettes and drinking alcohol are other risk factors for colorectal cancer.
Pictures & Images
Barium enema
The barium enema is a valuable diagnostic tool that helps detect abnormalities in the large intestine (colon). The barium enema, along with colonoscopy, remain standards in the diagnosis of colon cancer, ulcerative colitis, and other diseases of the colon.
Colonoscopy
There are 4 basic tests for colon cancer: a stool test (to check for blood); sigmoidoscopy (inspection of the lower colon; colonoscopy (inspection of the entire colon); and double contrast barium enema. All 4 are effective in catching cancers in the early stages, when treatment is most beneficial.
Digestive system
The esophagus, stomach, large and small intestine, aided by the liver, gallbladder and pancreas convert the nutritive components of food into energy and break down the non-nutritive components into waste to be excreted.
Rectal cancer, x-ray
A barium enema in a patient with cancer of the rectum.
Sigmoid colon cancer, x-ray
A barium enema in a patient with cancer of the large bowel (sigmoid area).
Spleen metastasis – CT scan
This CT scan of the upper abdomen shows multiple tumors in the liver and spleen that have spread (metastasized) from an original intestinal cancer (carcinoma).
Structure of the colon
The large intestine is a long hollow organ lined with mucous membrane (mucosa). Muscle layers wrap around the entire length and help move food material through to the rectum.
Large intestine
The large intestine is the portion of the digestive system most responsible for absorption of water from the indigestible residue of food. The ileocecal valve of the ileum (small intestine) passes material into the large intestine at the cecum. Material passes through the ascending, transverse, descending and sigmoid portions of the colon, and finally into the rectum. From the rectum, the waste is expelled from the body.
Stages of cancer
The staging of a carcinoma has to do with the size of the tumor, and the degree to which it has penetrated. When the tumor is small and has not penetrated the mucosal layer, it is said to be stage I cancer. Stage II tumors are into the muscle wall, and stage III involves nearby lymph nodes. The rare stage IV cancer has spread (metastasized) to remote organs.
The large intestine
The large intestine (or colon, or large bowel) is the last structure to process food, taking the undigestible matter from the small intestine, absorbing water from it and leaving the waste product called feces. Feces are expelled from the body through the rectum and the anus.
Colon polyps
When polyps are discovered in a sigmoidoscopy (an inspection of the lower third of the large intestine), they are retrieved to be tested for cancer. If a large amount of polyps are found, a more thorough examination of the entire length of the large intestine (a colonoscopy) may be recommended.
Colon cancer – series
Normal anatomy
The colon, or large intestine, is a muscular tube that begins at the end of the small intestine and ends at the rectum. The colon absorbs water from liquid stool that is delivered to it from the small intestine.
Colon cancer – series
Indication
Colon cancer is the third most common cancer in the United States. Risk factors include a diet low in fiber and high in fat, certain types of colonic polyps, inflammatory bowel disease (such as Crohn’s disease or ulcerative colitis), and certain hereditary disorders.
Colon cancer – series
Incision
The treatment of colon cancer depends on the stage of the disease. Stage I cancer is limited to the inner lining of the colon; stage II cancer involves the entire wall of the colon; stage III cancer has spread to the lymph nodes; stage IV cancer has spread to other organs (metastasized).
Colon cancer – series
Procedure
Surgery is the main treatment for colon cancer and removal of the involved colon is required. If the cancer is located near the rectum, a colostomy may be necessary. For stage I and II colon cancer, surgery is usually the only treatment. For stage III or IV colon cancer, chemotherapy is necessary after surgery. There is also some suggestion that chemotherapy may also be helpful in some selected stage II patients. Chemotherapy involves a course of drugs which are toxic to cancer cells.
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Colon cancer : Overview, Causes, & Risk Factors
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Colon cancer : Symptoms & Signs, Diagnosis & Tests
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Colon cancer : Treatment
Review Date : 11/5/2009
Reviewed By : David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital.
