Polyps and Dysplasia
Doctors think that all cases of colon cancer originally begin as small growths called polyps, according to GIHealth.com. These polyps are benign, which means that they are not cancerous. The cells in these polyps, however, have already begun to grow rapidly, which means that they are abnormal and could become cancerous. There are four types of polyps. Inflammatory polyps are common in patients with inflammatory bowel disease and are not thought to be related to cancer. Hyperplastic polyps are small and are also considered to be low risk to develop into cancer. Adenomatous polyps are the most common type of polyp and grow slowly. As they get larger, however, the risk of them progressing into cancer increases, so they should be removed. The final type of polyp is a tubulovillous adenoma, which carries a higher risk of becoming cancerous. These polyps can be more difficult to remove and may require surgery.
Carcinoma In Situ
The earliest stage of colon cancer, according to the American Cancer Society, is called carcinoma in situ (or intramucosal carcinoma). This type of cancer is the least serious because it has not spread past the inner layer of the lining of the colon (also known as the mucosa). The National Cancer Institute also notes that this form of colon cancer is called stage 0 cancer. Because stage 0 cancer is confined to the lining of the colon, it can be treated via surgery.
Advanced Disease
Although stage 0 cancer itself is not particularly dangerous, it has the potential to invade other tissues, leading to more serious forms of colon cancer. As colon cancer invades deeper into other tissues, it becomes more difficult to treat. The American Cancer Society explains that colon cancer is referred to as stage I when it has spread through the muscular inner lining (muscularis mucosa) of the colon. Stage II disease has spread further throughout the lining of the colon and has infiltrated another ring of muscle tissue, called the muscularis propia, that represents the outer margin of the colon. Stage III cancer, the National Cancer Institute explains, has infiltrated the lymph nodes. Stage IV cancer (also known as metastatic colon cancer) is the most serious form of colon cancer because the cancer has spread to distant organs. These distant metastases can spread to the liver, lungs and throughout the abdomen and can cause fatal organ dysfunction.
