Overview Colorectal cancer is a disease in which normal cells in the lining of the colon or rectum begin to change, start to grow uncontrollably, and no longer die. Initially, the cell growth appears as a benign (noncancerous) polyp that can, over time, become a cancerous tumor. If not treated or removed, a polyp can become a potentially life-threatening cancer.
• Benign. Cells of benign tumors stay in one area and do not invade other tissue or spread to other parts of the body.
• Malignant. Malignant tumors contain cells that continue to divide uncontrollably and usually have an irregular shape and structure. They can invade other tissue and spread to other parts of the body.
The majority of polyps originating in the mucosal lining of the colon are benign colorectal tumors. Adenomatous polyps, however, have the capacity to become cancerous if they are not removed and may transform into a growth that can divide and spread. Malignant tumors that invade the walls of the large intestine are referred to as colorectal cancers or colorectal carcinoma. Most cancers of the large intestine evolve from polyps.
In advanced stages of colorectal cancer, the malignant cells may grow through the walls of the colon and move through the bloodstream to other parts of the body, such as the liver, abdomen or lung, causing cancer to develop in these organs. At this stage, the cancer is termed a metastatic malignancy. During this metastatic process, some cancerous cells may be filtered and held by the lymph nodes, which provide an indication of how far the cancer has spread.
Back to Top Symptoms Early symptoms are not evident in one-third of patients with colon cancer. Symptoms may not become noticeable until a cancerous tumor is large enough (about the size of a pea or 1 centimeter) to affect surrounding tissue. The most common symptoms that need to be reported to your physician include:
Change in bowel habits that lasts for more than a few days, including constipation or diarrhea, narrowing of stool and a feeling of fullness that continues after having a bowel movement. These changes can be due to an obstruction caused by the growth of a tumor. Bleeding is the most common symptom of colorectal cancer. The bleeding is the result of irritation of the tumor by the passage of stool. Blood may be hidden (occult) or appear visibly in the stool, depending on the location of the tumor. If the tumor is near the rectum, the blood will be visible. If it occurs further back in the colon, it will be occult. Tumors in the descending or sigmoid colon may result in streaks of blood in the stool.
Abdominal pain can result from a stretching of the large intestine by the growth of a tumor. The enlarged colon presses against nerves and other tissue, causing discomfort. A cramping sensation may be experienced, especially after eating. Sometimes a tumor is found in the colon of patients who go to their doctor for pain in some other abdominal organ such as the liver.
Decreased appetite, loss of weight, and weakness may also be symptoms of colorectal cancer.
Treatment The type of treatment selected will depend upon tumor grade and stage as well as your general health. Four types of treatment are commonly used for colorectal cancer: surgery, radiation, chemotherapy, and targeted therapy.
