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Colon Cancer

Last Updated: Mar 1, 2019


Colon cancer (also called colorectal cancer) is cancer of the large intestine, including the colon and rectum. All cancers begin when cells grow uncontrollably to form a clump of cells referred to as a tumor. Benign tumors are not life-threatening and can be removed when they cause discomfort. Cancerous (or malignant) tumors, however, can spread to other organs (metastasize) via the body’s circulatory system. Colorectal cancer is 90% curable if detected early.

The intestinal wall consists of five layers: mucosa, submucosa, muscle, subserosa, and serosa. Over 95% of all colon cancers are adenocarcinomas, which occur in the mucus-producing cells of the mucosa lining. Adenocarcinomas begin in the form of an abnormal growth called a polyp; however not all polyps are pre-cancerous.

Colorectal cancer affects both men and women as the third most common cancer. In the United States, colon cancer is the second leading cause of cancer-related deaths.

Causes and Risk Factors

Large and small intestines

All cancers start with errors, or mutations, in the DNA of our cells. While some mutations are harmless, others can interrupt the processes that regulate cell division and maintenance, hence allowing uncontrolled cell growth. While the detailed mechanisms that lead to colon cancer onset are not fully understood, the following risk factors should be considered:


As colon cancer advances, it can produce the following symptoms:


Early screening and diagnosis of colon cancer are carried out using the following methods:

Once a cancer is diagnosed, it is then “staged” to assess the extent of spread within the body. In order to stage cancer, various imaging techniques (CT scan or X-ray) and surgery are performed. Adenocarcinomas are typically staged from 1-4 (represented as Roman numerals I-IV). A stage 0 designations means the cancer has not spread beyond the mucus lining of the colon.


Treatment options vary per patient and depend to a great extent on the disease stage; an early stage cancer has the best chances for a favorable outcome. Cancer is typically treated using a combination of approaches that are designed to kill and remove the affected cells. The 5-year survival rates for colon cancer ranges from 74% (stages I) to 6% (stage IV).


Colon cancer screening in people over the age of 50, or those with known risk factors, is key to early detection. The risk of developing colon cancer can be reduced by refraining from smoking; maintaining a healthy weight; and eating a diet that is high in fruits and vegetables, but low in fat.


Additional Resources

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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.