Colon Cancer Basics

What is Colon Cancer?

Female doctor examining a young man
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What is Cancer?

To understand what colon cancer is, it helps to start with a basic understand of cancer in general. Normal cells in the body grow and divide in an orderly fashion. Eventually, they die and are replaced by new, healthy cells. But cancer cells play by different rules—they don’t grow in an orderly fashion and they don’t die in an orderly fashion either.

Cancer cells no longer respond to the signals that tell them to grow and divide normally, which allows them to grow out of control. Cancer cells also are ‘immortal’: they have the ability to continue living indefinitely. Even when damaged in a way that should cause cell death, cancer cells may not die.

What is the Colon?

The colon is an important part of the digestive system, and as such, it has a major role in helping the body absorb nutrients, minerals, and water. The colon also helps rid the body of waste in the form of stool. The colon makes up the majority of the large intestine, approximately six feet in length. The last six inches or so of the large intestine are the rectum and the anal canal.

What is Colon Cancer?

Colon cancer is cancer that occurs in the cells of the colon. Colon cancer is quite common, being the third most common cancer in men and women in the U.S. About 110,000 people in the U.S. are diagnosed with colon cancer each year.

Some health experts consider colon and rectum cancers as one group, called colorectal cancer. Others treat these two cancers as completely separate: colon cancer and rectum (rectal) cancer.

In addition to the approximately 110,000 new cases of colon cancer each year, there are an additional 40,000 cases of rectal cancer, bringing the combined total of colon and rectal (colorectal) cancer to approximately 150,000 new cases per year.

Types of Colon Cancer

About 95% of all colon cancers are adenocarcinomas. The other 5% of colon cancers are made up of less common cell types including neuroendocrine tumors, gastrointestinal stromal tumors (GISTs), carcinoid tumors, lymphomas, melanomas, leiomyosarcomas, and signet ring cell tumors.

Some of these cell types may sound familiar to you, because they occur in other parts of the body, too. For example, melanoma most commonly occurs in the skin, but it can occur in the colon and other areas, as well.

Stages of Colon Cancer

In order for your doctor to develop the right treatment plan, he or she will stage your colon cancer. The stage of cancer refers to how far it has spread beyond the location where it first developed in your body.

Generally, the higher the number or letter that is used to describe the stage of cancer, the more advanced the cancer is. To learn more about colon cancer staging, be sure to review Diagnosis of Colon Cancer and Treatment of Colon Cancer.

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