The vast majority of colon cancers arise from the glandular cells lining the wall of the organ, in which case they are classified as a special type of carcinoma known as adenocarcinomas. Colon cancers can also originate in other cell types, such as those that comprise the connective tissue that supports the colorectal wall or those that are specialized for producing hormones.

Each year in the United States about 50,000 people die from colon cancer, making it one of the leading causes of cancer-related death in the country. In some other parts of the world, such as Asia and Africa, colon cancer is much less common, a fact often attributed to the Western diet, which tends too be high in fat and low in fiber.

In addition to diet, a number of other risk factors for developing colon cancer have been identified. Genetics is thought to be particularly important, those with a close family member diagnosed with the disease being three times more likely than others to develop colon cancer. Various inherited conditions, the most notable of which are familial polyposis syndrome and familial colon cancer, also greatly increase the disease risk, as do the presence of benign polyps in the colon. Benign polyps, which can become malignant over time, are consequently often removed if they come to the attention of a medical professional.

As is generally the case with cancers, colon carcinoma is easiest to treat and is associated with the best prognosis whenever the disease is diagnosed early in its development. Unfortunately, symptoms of colon cancer do not usually appear until the disease is significantly advanced, and even then are generally non-specific so that individuals may not immediately seek medical attention. Diarrhea, constipation, abdominal pain, and appearance of blood in the stool are typically among the first signs that something is wrong. Later, jaundice, fluid accumulation in the abdomen (ascites), and shortness of breath may develop as well.

Routine screening for colon cancer is often recommended for individuals 50 years of age or older. This procedure generally consists of a fecal occult blood test, which can reveal the presence of blood in fecal material even when it cannot be detected by the eye, and flexible sigmoidoscopy, which involves the use of a tube-like instrument to inspect the rectum and lower colon. Individuals known to be at high risk for the disease may also be advised to periodically undergo the more extensive examination known as a colonoscopy, in which the condition of the entire colon can be assessed. Diagnosis of colon cancer often initially involves the same techniques utilized for screening purposes, but a biopsy is needed to confirm the presence of cancer cells.

The primary treatment for most colon cancer patients is surgery. In some cases, tumors can be removed through colonoscopic means, but most commonly surgical resection is needed. For some patients, a colostomy is necessary for bodily waste removal following surgery. Radiation therapy and chemotherapy are often used as adjuvants to surgery, but are occasionally the primary means of treatment, especially in individuals that are unable to undergo surgery for health reasons. The side effects of these forms of therapy can be intense because they target all rapidly dividing cells, not just cancer cells.

Colon Carcinoma at 10x Magnification - The link between diet and colon carcinoma is supported by statistics that indicate that in countries whose inhabitants are increasingly eating like Americans, colon cancer rates are rising.

Colon Carcinoma at 40x Magnification - The irritable bowel disease known as ulcerative colitis, which is characterized by inflammation and ulceration, increases colon cancer risk in individuals in which it is a chronic occurrence.

Colon Carcinoma at 10x Magnification - Typically tumors of the colon have grown to sizes of several centimeters by the time symptomatic evidence and testing result in a diagnosis of the disease.

Colon Carcinoma at 40x Magnification - A number of imaging techniques, including x-rays, magnetic resonance imaging (MRI) and computed tomography (CT) scans, are commonly used during the staging of colon cancer.