Colon cancer is a malignant growth that is found in the colon, which is part of the digestive system. The colon is also called the large intestine in layman’s terms. Colon cancer usually starts as a small growth or polyp. These polyps could be non-cancerous but doctors always recommend that they are removed as early as possible just in case. Sometimes the term used for this cancer is colorectal cancer which includes both cancers of the colon and the rectum. There is no identified cause for colon cancer though it is believed that a genetic mutation of the cells causes the uncontrolled multiplication of the cells.

Diagnosis
When a doctor finds that the patient has symptoms that might indicate colon cancer or polyps, a colonoscopy is performed. Any suspicious polyps can be biopsied to study for potential problems. Sometimes colon cancers produce a chemical called a carcinoembryonic antigen, or CEA that can be studied through a blood test. When the patient has undergone treatment for cancer, further blood tests can study how effective the treatment has been in fighting cancer.

The Main Stages of Colon Cancer
When it is confirmed that a patient has colon cancer, a doctor will perform further tests to study and classify the extent to which cancer has progressed. This helps to get a clear picture of the disease and the best line of treatment. Though the colon can be studied through scans, most times the actual extent of the cancer is clearly determined during surgery.

The main stages of colon cancer are denoted using the numbers zero to four in Roman numerals. The staging is usually as per the American Joint Committee on Cancer (AJCC) TNM system. This system uses three factors that are denoted by alphabets T, N, and M.

• The alphabet T indicates the extent of tumor growth. The classification of T is determined based on how far the tumor has grown through the subsequent layers of the colon: the mucosa or inner lining, the muscularis mucosa or thin muscle lining, the submucosa, muscularis propria or the thick muscle layer or the outermost connective tissue layers of the colon called the subserosa and serosa, respectively. These outer connective tissue layers are not present in the rectum.
• The alphabet N indicates whether cancer has spread to the nearby lymph nodes. The value of N is higher if the cancer is found to have spread to lymph nodes or sites in the body.
• The M component of classification indicates metastasis or whether cancer has spread to other areas of the body. Stage 0 is when the cancer is limited only to the lining of the colon. The highest stage indicates that the colon cancer has spread or metastasized to the rest of the body.

Based on the values of TNM, the cancer is assigned one out of a series of main stages of colon cancer.